CRANIAL NERVE PALSY
CRANIAL NERVE III PALSY
SIGNS AND SYMPTOMS
The patient will usually present with sudden onset unilateral ptosis (or rarely, a bilateral ptosis if the damage occurs to the third nerve nucleus), which is frequently accompanied by significant eye or head pain. The patient rarely complains of double vision because the ptosis obscures the vision in the affected eye; however, if the lid is manually elevated, the patient will experience diplopia. Acuity is typically unaffected unless damage occurs in the superior orbital fissure and cranial nerve II is also involved. The affected eye positions in a non-comitant exotropic, hypotropic position (down and out).
There will be limitation of elevation, depression and adduction. There is an underaction of the superior, inferior, and medial recti muscles and inferior oblique muscle, which may be total or partial. The pupil may be dilated and minimally reactive to light (pupillary involvement), totally reactive and normal (pupillary non-involvement), or may be sluggishly responsive (partial pupillary involvement). The patient is frequently elderly and often has concurrent diabetes and/or hypertension.
Third nerve palsy results from damage to the oculomotor nerve anywhere in its course from the nucleus in the dorsal mesencephalon, its fascicles in the brainstem parenchyma, the nerve root in subarachnoid space, or in the cavernous sinus or posterior orbit. Damage to the third nerve nucleus results in an ipsilateral third nerve palsy with contralateral superior rectus under action and bilateral ptosis. Damage to the third nerve fascicles results in an ipsilateral third nerve palsy with contralateral hemiparesis (Weber's syndrome), contralateral intention tremor (Benedikt's syndrome), or ipsilateral cerebellar ataxia (Nothnagel's syndrome). Vascular infarct, metastatic disease and demyelinization are the common causes of brainstem involvement.
Damage to the third nerve within the subarachnoid space produces an isolated third nerve palsy. The main causes are compression of the nerve by an expanding aneurysm of the posterior communicating artery or the basilar artery, and ischemic vasculopathy. There will always be pain in aneurysmal compression and pupillary involvement is typical, though there have been infrequent cases of aneurysmal compression that did not initially affect pupillary function. In ischemic vascular nerve third palsies, pain is frequent and the pupil is typically normal and reactive.
Damage to the third nerve in the cavernous sinus, superior orbital fissure, or posterior orbit is unlikely to present as third nerve palsy due to the confluence of other structures in these areas. Cavernous sinus involvement may also include pareses of cranial nerves IV, VI and V-1, and an ipsilateral Horner's syndrome. The most common causes of damage in these areas include metastatic disease, inflammation, herpes zoster, carotid artery aneurysm, pituitary adenoma and apoplexy, and sphenoid wing meningioma.
In complicated third nerve palsies where other neural structures are involved, have the patient undergo an MRI. In isolated third nerve palsies with no pupillary involvement where the patient is over 50, MRI scanning, an ischemic vascular evaluation, and daily pupil evaluation is indicated.
If the patient is under 50 and has a non-pupillary involved isolated third nerve palsy, intracranial angiography is indicated since ischemic vasculopathy is less likely to occur in this age group than is aneurysm. If the adult patient of any age presents with a complete or incomplete isolated third nerve palsy with pupillary involvement, consider this to be a medical emergency and have the patient undergo intracranial angiography immediately. In these cases, the cause is likely subarachnoid aneurysm and the patient may die if the aneurysm ruptures. Children under the age of 14 rarely have aneurysms; the majority of third nerve palsies in this age group are traumatic or congenital.
Isolated third nerve palsy due to ischemic vasculopathy will spontaneously resolve and recover over a period of three to six months. If the palsy fails to resolve in this time frame, repeat the MRI to search for the true etiology.
Myasthenia gravis has the ability to mimic virtually any cranial neuropathy, including isolated third nerve palsies. Myasthenia gravis must remain a possible diagnosis when encountering a third nerve palsy, especially when the course is variable or atypical.
CRANIAL NERVE IV PALSY
SIGNS AND SYMPTOMS
The patient will present with complaints of vertical diplopia, which is especially manifest as the patient tries to read. There may be an inability to look down and in. There may also be horizontal diplopia, as a lateral phoria occurs due to the vertical dissociation. The patient often has a head tilt contralateral to the affected superior oblique muscle. The chin is often tucked downwards as well. There is frequently concurrent hypertension and/or diabetes. The patient will present with a hyperphoric or hypertropic eye on primary gaze. On alternate cover test, the hyper-deviation will increase in contralateral gaze, reduce in ipsilateral gaze, increase on ipsilateral head tilt, and decrease on contralateral head tilt. Visual acuity is unaffected and there is very rarely pain. In bilateral cranial nerve IV palsy, the patient will manifest a hyper-deviation which reverses in opposite gaze.
The fourth cranial nerve nucleus is located in the dorsal mesencephalon. From here, the nerve fibers then decussate and exit the brain stem dorsally into the subarachnoid space. The nerve then courses around the brain to enter the cavernous sinus, superior orbital fissure, orbit, and innervate the superior oblique muscle. Damage to the fourth nerve nucleus or its fascicles within the brain stem will give a contralateral fourth nerve palsy, along with the associated signs of light-near dissociated pupils, retraction nystagmus, up-gaze palsy, Horner's syndrome, and/or internuclear ophthalmoplegia. Bilateral fourth nerve palsies are possible as well. The main causes of damage to the fourth nerve in this area are hemorrhage, infarction, trauma, hydrocephalus and demyelinization.
The fourth nerve is especially prone to trauma as it exits the brain stem and courses through the subarachnoid space. In contrast to third nerve palsies within subarachnoid space, fourth nerve palsies are rarely due to aneurysm. The most common causes of damage to the fourth nerve in this region are trauma and ischemic vasculopathy. The most likely result from damage within subarachnoid space is an isolated fourth nerve palsy.
Due to the large number of other neural structures that accompany the fourth nerve as it travels through the cavernous sinus and superior orbital fissure, it is unlikely that the patient will exhibit an isolated fourth nerve palsy due to damage within these areas. More likely, there will be an associated palsy of cranial nerves III and VI. Common causes of damage to the fourth nerve in these areas are herpes zoster, inflammation of the cavernous sinus or posterior orbit, meningioma, metastatic disease, pituitary adenoma, and carotid cavernous fistula. Trauma to the head or orbit can cause damage to the trochlea, resulting in superior oblique muscle dysfunction.
A fourth nerve palsy often presents suddenly, but may additionally result from decompensation of a longstanding palsy. In order to differentiate these two types of palsies, examine old photographs of the patient. A patient with a decompensated longstanding palsy will present with a compensatory head tilt in old photos. Further, patients with decompensated longstanding fourth nerve palsies will have an exaggerated vertical fusional ability. Longstanding fourth nerve palsies typically are benign and no further management is necessary.
In the case of complicated fourth nerve palsies, (i.e., those that present with other concurrent neurological dysfunction), the patient should undergo neuroradiological studies dictated by the accompanying signs and symptoms. In the case of isolated fourth nerve palsies caused by recent trauma, the patient should undergo an MRI or CT scan of the head to dismiss the possibility of a concurrent subarachnoid hemorrhage. If the fourth nerve palsy is not associated with recent trauma, investigate for a history of past trauma. If the fourth nerve palsy is due to previous trauma and has recently decompensated, you can manage the diplopia with vertical prisms.
If the patient is elderly and has a fourth nerve palsy of recent origin, perform an ischemic vascular evaluation to search for diabetes and hypertension. If the palsy is caused by vascular infarct, it will spontaneously resolve over a period of three to six months and the patient will not require further management beyond periodic observation and either temporary occlusion or press-on prism therapy.
Consider cases of true vertical diplopia to be a fourth nerve palsy until proven otherwise. In children, nearly all cases of isolated fourth nerve palsy are either congenital or traumatic in nature. In adults, approximately 40 percent of all isolated fourth nerve palsies are traumatic, 30 percent are idiopathic, 20 percent are due to vascular infarct, and only 10 percent are due to tumor or aneurysm.
The vast majority of fourth nerve palsies are benign. When encountering a sudden-onset isolated fourth nerve palsy, delay prescribing permanent prisms for at least three months in order to allow the palsy to recover
CRANIAL NERVE VI PALSY
SIGNS AND SYMPTOMS
The patient will present with horizontal uncrossed diplopia which worsens at distance and in either right or left gaze. The patient will have an abduction deficit in the involved eye and either an esophoric or esotropic position which is non-comitant. The onset is typically sudden. If the palsy is isolated, there will be neither visual acuity nor visual field loss. There may be some degree of head pain. The patient typically is older and has a concurrent history of hypertension and/or diabetes. The fundus is typically normal, except when the patient manifests a bilateral cranial nerve VI palsy, where there typically will also be papilledema.
Cranial nerve VI arises in the pons, in close association with the facial nerve and paramedian pontine reticular formation (PPRF). Due to this arrangement, damage to the sixth nerve within the brain stem will produce a sixth nerve palsy as well as a facial nerve palsy or an internuclear ophthalmoplegia. Associated findings may also include leg paralysis with sixth nerve palsy (Raymond's syndrome), or leg paralysis, facial paralysis and sixth nerve palsy (Millard-Gubler syndrome). These additional findings identify the location of damage as the pons, where ischemic infarct, tumor and demyelinization are the common causes.
The sixth nerve travels through the subarachnoid space where it ascends the clivus and enters the cavernous sinus. Within the subarachnoid space, the sixth nerve may be stretched against the clivus as the brain stem herniates through the foramen magnum due to increased intracranial pressure. This will give a bilateral sixth nerve palsy (which is often intermittent) and papilledema. As the sixth nerve passes over the petrous apex of the temporal bone, damage here can result in a sixth nerve palsy, facial pain and hearing loss. This occurs due to inflammation of the temporal bone (Gradenigo's syndrome) or nasopharyngeal carcinoma.
Within the cavernous sinus, the sixth nerve is joined by the oculosympathetic nerves, and cranial nerves III, IV and V-1. Damage here will yield a sixth nerve palsy and Horner's syndrome, as well as a concurrent CN III and IV palsy. The etiology may be aneurysm, meningioma, pituitary adenoma, inflammation, or fistula. The sixth nerve is also vulnerable to ischemic infarct from diabetes and hypertension; this remains a prime cause of isolated sixth nerve palsy.
A sixth nerve palsy combined with any of the above mentioned neurological signs indicates a need for MRI of the appropriate area. In children, sixth nerve palsy often occurs from a presumed viral cause and has an excellent prognosis. However, if the palsy does not recover, or worsens over several weeks, the child should be examined for a pontine glioma. In the adult under 50 years, obtain MRI studies of the brain. Adult over 50 with an isolated sixth nerve palsy require a workup for ischemic vascular diseases such as diabetes and hypertension. If the patient is over the age of 65 years, order an erythrocyte sedimentation rate (ESR) to rule out giant cell arteritis.
If no etiology is discovered on MRI or hematology studies, monitor the patient monthly for several months until resolution (or until other signs develop which would indicate an etiology). The vast majority of CN VI palsies due to ischemic vasculopathy (or idiopathic etiology) will resolve without treatment in three to six months. Fresnel prism correction or unilateral occlusion will temporarily alleviate the diplopia.
The etiology of isolated CN VI palsy in adults is undetermined in 25 percent of cases, despite full diagnostic evaluation. These palsies, and those due to diabetes or hypertension, resolve in three to six months without treatment. A diagnostic workup should include intracranial MRI, CBC with differential, fasting blood glucose, ESR, blood pressure measurement, Lyme titer and syphilis serology. If these tests are negative, monitor the patient for resolution. Clinical worsening over time indicates the need for more thorough or repeat investigation.
Myasthenia gravis may mimic a sixth nerve palsy and should always be considered in the differential diagnosis, especially if the palsy takes on a variable course with exacerbations and remissions. Always consider the possibility of myasthenia gravis in cases of non-restrictive, pupil sparing CN III, IV and VI nerve palsy as well as unilateral and bilateral internuclear ophthalmoplegia.
CRANIAL NERVE VII (FACIAL NERVE) PALSY
SIGNS AND SYMPTOMS
The prevalence of idiopathic cranial nerve VII (CN VII) palsy ranges from 10/100,000 to 40/100,000 with an average of 21/100,000. Occurrences are highest in adults over 70. Recurrence of idiopathic CN VII palsy ranges between 6 to 11 percent.
Cranial nerve VII innervates the muscles of facial expression and the stapedius muscle of the inner ear. The orbicularis oculi, responsible for eyelid closure, is controlled by CN VII. Damage to the nerve or its peripheral course produces weakness or paralysis of one side of the face with an inability to close the ipsilateral eye. Additional findings on the affected side include flattening of the nasal labial fold, droop of the corner of the mouth, ectropion, lagophthalmos, decreased tear production, dry eye, conjunctival injection, corneal compromise, decreased sense of taste and hyperacusis (supersensitivity to sound).
Occasionally, following injury, some fibers of CN VII regenerate to erroneously innervate adjacent structures. The result is simultaneous movements of muscles (e.g. the corner of the mouth contracts on attempted eyelid closure) or the stimulation of glands supplied by the redistributed branches of CN VII when the nerve is activated (e.g. excessive lacrimation upon eating, known as crocodile tearing ).
The muscles that close the eyes and wrinkle the forehead are bilaterally innervated. A unilateral lesion in the cortex or supranuclear pathway spares eyelid closure and forehead wrinkling but results in contralateral paralysis of the lower face. Since the area of the cortex associated with facial muscle function lies near the motor representation of the hand and tongue, weakness of the thumb, fingers and tongue ipsilateral to the facial palsy is not uncommon.
The facial nucleus contains four separate cell groups that innervate specific muscle groups. Lesions of the fibers of the superior salivatory and lacrimal nuclei (parasympathetic preganglionic fibers supplying the sublingual, submandibular and lacrimal glands) include temporal bone fractures and infections, schwannomas, neuromas (cerebellopontine angle tumors) and vascular compression, producing deficits in hearing, balance, tear production and salivatory flow.
Lesions that involve the ganglion include geniculate ganglionitis (Ramsey-Hunt syndrome: zoster oticus). Lesions such as acoustic neuroma that also involve cranial nerve VIII can impair hearing, facial nerve function and produce corneal hypoesthesia (CN V).
Lesions of the zygomatic and lacrimal nerves impair reflex tear secretion. Middle cranial fossa disease is indicated when defective tear production accompanies CN V (muscles of mastication) or CN VI palsy.
Lesions of the facial nerve disable the ability to dampen sound, producing hyperacusis. Lesions to sensory afferent fibers that transmit taste (fibers that also innervate the salivary glands) cause an interruption in salivatory flow and an inability to sense taste from the anterior two-thirds of the tongue.
The portion of the facial nerve that contains the motor fibers that innervate the muscles of facial expression exits the stylomastoid foramen and enters the substance of the parotid gland before distribution. Therefore, investigate lesions of the parotid gland also as part of the work up.
Lesions that occur within the cortical, extrapyramidal or brainstem levels are known as central lesions. Lesions outside the brain are referred to as peripheral. The common causes of peripheral CN VII palsy include cerebellopontine angle tumor (7 percent), trauma (21 percent), otitis media, herpes zoster oticus (Ramsey-Hunt syndrome), Lyme disease, sarcoidosis, parotid neoplasm, syphilis, diabetes mellitus, pregnancy and HIV.
First obtain a complete history. Perform a cursory evaluation of the 12 cranial nerves as well as a comprehensive ocular examination with dilated fundus and optic nerve evaluation. Pay close attention to the affected eyelid's posture, corneal wetting (tear break up time), blink posture, tear quality (sodium fluorescein staining) and tear quantity (Schirmer tear testing). In cases where diagnosis is questionable, ask the patient to close both eyes while you try to open the lid. If one lid is significantly easier to open than the other, suspect CN VII palsy.
You can manage exposure keratopathy with ocular lubricating drops and ointments. Moisture chamber patches (e.g. Guibora eye patch) or eyelid taping are also possible solutions. Moisture chamber shields can be attached to spectacle temples to create a moist ocular environment and lessen tear evaporation. Since idiopathic facial nerve palsy is a diagnosis of exclusion, order laboratory testing (Lyme titer, rheumatoid factor, erythrocyte sedimentation rate, antinuclear antibody, echocardiogram, fluorescent treponemal antibody absorption test, HIV titer, chest X-ray), lumbar puncture (in patients with suspected neoplasm), CT and MRI and/or appropriate referrals (otolaryngology, neurology, neurosurgery).
Most cases (53 percent) of unilateral facial weakness are idiopathic. These lesions are thought to occur secondary to idiopathic inflammation, viral infection or vascular compression of CN VII. Given the extensive neurology of CN VII, idiopathic "Bell's Palsy" is a diagnosis of exclusion.
Patients with idiopathic facial nerve paralysis (Bell's Palsy) typically complain of acute (24 to 48 hours) unilateral facial weakness with a widening of the palpebral fissure and impaired ability to close the eye.
Risk factors include diabetes, pregnancy and family history.
Chronic, slowly progressive facial nerve palsy suggests neoplasm. The presence of a parotid mass suggests tumor of the gland.
Paralysis of the lower face that spares eyelid closure and forehead wrinkling indicates a lesion in the contralateral cerebral cortex.
SIGNS AND SYMPTOMS
Several underlying systemic diseases can cause this condition. There is a painless onset of visual disturbance, but often no diplopia in primary gaze. There will be horizontal diplopia in lateral gaze. The patient will manifest an adduction deficit on the involved side and a nystagmus of the fellow eye in extreme abduction.
Occasionally, the condition is bilateral with medial rectus palsy and adduction deficit in each eye and nystagmus upon abduction in both eyes (bilateral internuclear ophthalmoplegia, or BINO) While there appears to be medial recti palsy, most patients will be able to converge (posterior INO or BINO). In some cases, the patient will not be able to converge (anterior INO or BINO).
To produce synchronous eye movements, cranial nerves III, IV and VI communicate through the medial longitudinal fasciculus (MLF), the neural pathway connecting the cranial nerve nuclei responsible for eye movements. In INO, a lesion disrupts this pathway, preventing communication between cranial nerves.
For example, for a patient to gaze to the left, the left supranuclear control center of horizontal eye movements [paramedian pontine reticular formation (PPRF)] must signal the left CN VI nucleus to turn the left eye outwards. At the same time, the PPRF must signal the right CN III nucleus, via the right MLF, to simultaneously turn the right eye inwards. A lesion of the right MLF would not allow the neural impulse to reach the right medial rectus. In this case, the left eye would abduct, but the right eye would not adduct. Further, the left eye would go into an abducting nystagmus.
Most lesions of the MLF are located in the pons, or caudal mesencephalon. Thus, patients with INO or BINO will be able to converge (posterior INO/BINO). However, if the lesion affects the MLF within the mesencephalon and involves the CN III nucleus, then the patient will not be able to converge (anterior INO/BINO).
Possible causes of INO/BINO:
brainstem and fourth ventricular tumor
drug intoxication (phenothiazines and tricyclic antidepressants)
Typically, multiple sclerosis causes a bilateral presentation, whereas ischemic vascular infarction causes a unilateral episode. Also, myasthenia gravis can produce a pseudo-INO/BINO with a motility pattern identical to true INO/BINO.
Manage INO/BINO by identifying the underlying cause, and then obtaining appropriate medical treatment. In cases of ischemic vascular infarction, the motility pattern returns to normal over time. Appropriate testing includes MRI of the brainstem, FTA-ABS, VDRL, Lyme titre, fasting blood glucose, complete blood count with differential, blood pressure measurement, and toxicology screen.
Remember that myasthenia gravis can mimic the motility pattern of INO/BINO.
In younger patients, the etiology of INO/BINO is most commonly multiple sclerosis. In fact, INO/BINO is the most common ocular motility dysfunction in MS. Approximately 92 percent of patients who develop INO/BINO from demyelinization develop MS.
In older patients who develop INO/BINO, the most common etiology is ischemic vascular infarction. Beyond MRI studies, these patients need medical evaluation for ischemic vascular diseases such as diabetes and hypertension. These cases typically resolve over time.
SIGNS AND SYMPTOMS
Congenital pits of the optic nerve vary in size, shape, depth and location. They often appear as small, hypopigmented, yellow or whitish, oval or round excavated defects, most often within the inferior temporal portion of the optic cup. Approximately 20 to 33 percent are found centrally, with an average size of 500µm (one-third disc diameter).
Typically, optic pits occur unilaterally (85 percent). The optic disc in these patients appears larger than normal, and 60 percent of discs with optic pits also have cilioretinal arteries. These patients have a greater propensity to develop normal-tension glaucoma.
Most patients are unaware of the presence of an optic pit. Although as many as 60 to 70 percent of patients with optic pits possess some arcuate scotoma corresponding to the loss of retinal ganglion cells, their acuity is rarely affected. Patients may notice visual distortions, metamorphopsia or blurred vision. Those with temporal pits have the greatest risk for developing serous maculopathy.
The origin of optic pits remains unclear. Optic pits have been associated with colobomatous lesions, suggesting that they result from incomplete closure of the fetal fissure. Others propose that they result from abnormal differentiation of primitive epithelia papilla. Arcuate visual field defects are the result of corresponding loss of retinal ganglion cells or secondary atrophy of attenuated nerve fibers.
Some 40 to 60 percent of patients with optic pits develop non-rhegmatogenous serous macular detachments. These fluid-filled cystic maculopathies can develop into lamellar macular holes. The origin of the fluid is unknown. There is a high incidence of posterior vitreous detachment associated with these serous maculopathies.
Previous theories concerning the origin of the subretinal fluid seen in optic pit-related serous macular detachment include liquefied vitreous penetration and leaking vessels within the pit. New findings strongly suggest that serous macular detachments secondary to optic pits develop due to pre-existing schisis-like lesions which connect the macula to the optic disc. Fluid, predominantly from the outer plexiform layer, enters an already edematous retina through the optic pit via the retinal stroma, producing a macular detachment.
Begin the management of asymptomatic optic pit with a comprehensive eye examination, including threshold visual fields. Semi-annual intraocular pressure checks and dilated evaluations with drawings or photos are appropriate. Use home acuity assessment and home Amsler grid testing to monitor for the onset of maculopathy. Educate patients about the signs and symptoms of macular complications (e.g. blurred vision, visual distortions, metamorphopsia).
Treatment for optic pit-related macular detachment varies. Periodic monitoring, prophylactic laser photocoagulation, therapeutic laser photocoagulation after maculopathy has formed, oral steroids and vitrectomy have all been tried. The current trend is laser photocoagulation following the onset of maculopathy.
Differential diagnosis includes optic disc anomalies that mimic optic pit: choroidal and scleral crescent, tilted disc syndrome
, circumpapillary staphyloma, hypoplastic disc and glaucomatous optic neuropathy. Idiopathic central serous retinopathy and subretinal neovascular membrane are alternative considerations for serous macular detachment.
Any change in appearance of the optic pit over time suggests that the lesion may be an acquired notch of the neuroretinal rim secondary to glaucomatous processes.
SIGNS AND SYMPTOMS
The patient often complains of unequal pupil sizes, and frequently of decreased vision at near. The patient may be any age, especially if there has been history of local trauma or orbital surgery. Often when a history of trauma is not apparent, the patient will be younger and female.
A tonic pupil may occur in one or both eyes. It is typically larger than the normal fellow pupil in normal illumination. However, there is no significant change in size of the tonic pupil when going from bright to dim illumination. The tonic pupil will appear fixed and unreactive to light.
When testing near accommodation, the tonic pupil will show a slow constrictive response. Biomicroscopy often reveals segmental paralysis and flattening of the pupil border, which gives the pupil an irregular shape. There may also be a vermiform movement of the non-paralyzed sections of the iris. In cases of idiopathic tonic pupils, deep tendon reflexes often diminish, particularly in young females.
A tonic pupil results from damage to the ciliary ganglion within the orbit. In the ciliary ganglion, 93 percent of the post-ganglionic fibers innervate the ciliary body for accommodation; the remaining 7 percent innervate the iris sphincter for miosis during the light reflex. When the ciliary ganglion is damaged, there is an aberrant regeneration of fibers, with post-ganglionic fibers that originally innervated the iris sphincter now innervating the ciliary body. Thus, light response is diminished, but accommodative near constriction remains. However, near constriction is often slow and segmental, and accommodation is often diminished.
Trauma is the most common cause of a tonic pupil. Other causes associated with tonic pupils include viral illness, diabetes, syphilis and giant cell arteritis. When the etiology cannot be identified, particularly in young females, the condition is termed Adie's tonic pupil.
There is no exact management plan for tonic pupils. Address each case individually. If the patient dislikes the cosmetic asymmetry of the pupils, consider opaque contact lenses. For a patient over 60 who develops a tonic pupil, order an erythrocyte sedimentation rate (ESR) to check for giant cell arteritis. If the patient is male, and has bilateral tonic pupils, order both a specific (FTA-ABS) and non-specific treponemal (RPR) test to examine for syphilis. In most cases, try to elicit a history of trauma.
Remember that a tonic pupil in an elderly patient can be caused by giant cell arteritis, and order an ESR. This can help diagnose a vision-threatening disease before severe vision loss ensues from ischemic optic neuropathy.
Incidence of syphilis is about 45 percent in cases of bilateral tonic pupils in males. Order both a specific and non-specific treponemal test for diagnosis.
In cases of Adie's tonic pupils, testing of patellar tendon reflexes can assist in the diagnosis.
Not all tonic pupils are Adie's tonic pupils. This term is mistakenly overused. The term "Adie's tonic pupil" refers to an idiopathic tonic pupil.
Signs and Symptoms
Pseudotumor cerebri (PTC) is encountered most frequently in young, overweight women between the ages of 20 and 45. Headache is the most common presenting complaint, occurring in more than 90 percent of cases. Dizziness, nausea, and vomiting may also be encountered, but typically there are no alterations of consciousness or higher cognitive function. Tinnitus, or a "rushing" sound in the ears, is another frequent complaint. Visual symptoms are present in up to 70 percent of all patients with PTC, and include transient visual obscurations, general blurriness, and intermittent horizontal diplopia. These symptoms tend to worsen in association with Valsalva maneuvers and changes in posture. Reports of ocular pain, particularly with extreme eye movements, have also been noted.
Funduscopic evaluation of patients with PTC demonstrates bilaterally swollen, edematous optic nerves consistent with true papilledema. Ophthalmoscopy may reveal striations within the nerve fiber layer, blurring of the superior and inferior margins of the neural rim, disc hyperemia, and capillary dilatation. More severe presentations involve engorged and tortuous retinal venules, peripapillary hemorrhages and/or cotton wool spots, and circumferential retinal microfolds (Patonís lines). Chronic papilledema mayresult in atrophy of the nerve head, with associated pallor and gliosis. Most cases of true papilledema will not present with a relative afferent pupillary defect, although visual field deficits may be present. The most common visual field defect associated with PTC is an enlarged blind spot, followed by a nasal deficit, typically affecting the inferior quadrants. Other field losses seen in PTC include arcuate defects, nasal step, generalized constriction, and least commonly, cecocentral scotoma.
Pseudotumor cerebri is a syndrome disorder defined clinically by four criteria: (1) elevated intracranial pressure as demonstrated by lumbar puncture; (2) normal cerebral anatomy, as demonstrated by neuroradiographic evaluation; (3) normal cerebrospinal fluid composition; and (4) signs and symptoms of increased intracranial pressure, including papilledema.
While the mechanism of PTC is not fully understood, most experts agree that the disorder results from poor absorption of cerebrospinal fluid by the meninges surrounding the brain and spinal cord. The subsequent increase in extracerebral fluid volume leads to elevated intracranial pressure. However, because the process is slow and insidious, there is ample time for the ventricular system to compensate and this explains why there is no dilation of the cerebral ventricles in PTC. Increased intracranial pressure induces stress on the peripheral aspects of the brain, including the cranial nerves. Stagnation of axoplasmic flow in the optic nerve (CN II) results in papilledema and transient visual obscurations; when the abducens nerve (CN VI) is involved, the result is intermittent nerve palsy and diplopia.
Many conditions and factors have been proposed as causative agents of PTC, including excessive dosages of some exogenously administered medications (e.g., vitamin A, tetracycline, minocycline, naladixic acid, corticosteroids), endocrinologic abnormalities, anemias, blood dyscrasias, and chronic respiratory insufficiency. However the majority of cases remain idiopathic in nature.
All patients presenting with suspected papilledema or other manifestations of intracranial hypertension warrant prompt medical evaluation and neurologic testing. Current protocol dictates that patients presumptively diagnosed with papilledema must undergo neuroimaging via computed tomography or, preferably, magnetic resonance imaging within 24 hours. These tests are meant to rule out space-occupying intracranial mass lesions, and therefore should be ordered with contrast media unless otherwise contraindicated. In cases of PTC, neuroimaging typically displays small to normal-sized cerebral ventricles with otherwise normal brain structure. Patients with unremarkable radiographic studies should be subsequently referred for neurosurgical consultation and lumbar puncture. (Lumbar puncture should not be ordered until neuroimaging is found negative for space-occupying mass due to risk for herniation of brainstem through foramen magnum secondary to mass during lumbar puncture.) Additional medical testing includes serologic and hematologic studies.
Therapy for patients with PTC varies, but in most instances initiate systemic medications as a first line treatment. Typically, the drug of choice for the initial management of PTC is oral acetazolamide (Diamox), although other diuretics including chlorthalidone (Hygroton) and furosemide (Lasix) may also be used effectively. Corticosteroid therapy is considered controversial in the management of PTC. While a short-term course of oral or intravenous dexamethasone may be helpful in initially lowering intracranial pressure, it is not considered to be an effective long-term therapy because of the potential for systemic and ocular complications.
For patients in whom conventional medical therapy fails to alleviate the symptoms and prevent pathologic decline, surgical intervention is the only definitive treatment. Cerebrospinal fluid shunting procedures are commonly employed in recalcitrant cases of PTC, but are successful in only 70 to 80 percent of cases. Optic nerve sheath decompression has also been advocated as a method to alleviate chronic disc edema, although this technique fails to directly address the issue of elevated intracranial pressure. It also demonstrates a particularly high failure rate.
Optometric management of patients diagnosed with PTC includes careful and frequent evaluation, including threshold visual fields, acuity measurement, contrast sensitivity, and indirect ophthalmoscopy. Photodocu-mentation of the nerve heads should also be performed.
PTC is a diagnosis of exclusion.
Past literature refers to PTC as benign idiopathic intracranial hypertension, however this condition is far from benign. Patients may suffer intractable headache, severe nausea, intermittent diplopia and permanent vision loss, if they are not properly managed.
Although no single causative agent has been identified, it is clear that one very common factor in patients with PTC appears to be obesity in women of childbearing age. Interestingly, significant weight loss in conjunction with conventional therapy leads to complete remission of this disorder in many instances.
Patients with PTC should be enrolled in a formal weight-reduction program as a therapeutic measure.
While PTC occurs most commonly in females of childbearing age, a number of cases have been encountered in male children.
Amaurosis Fugax and Transient Ischemic Attack
Signs and Symptoms
Both amaurosis fugax (AF) and transient ischemic attack (TIA) are diagnosed almost exclusively by history alone. Patients with both AF and TIA are typically elderly with a history of diabetes, hypertension, or generalized atherosclerosis. Younger patients with these conditions may have a history of cardiac valve disease, blood constituent or coagulation abnormalities, or drug use.
Amaurosis fugax is a painless, monocular loss of vision, which may be total or sectorial. This is a traditional blackout of the patientís vision. Amaurosis fugax can occur in isolation, antecedent, or crescendo and is unprovoked and unpredictable. Vision loss typically lasts only seconds, but may last for hours and will resolve completely. There are no other neurological symptoms or findings in association with AF.
Transient ischemic attacks can result in a total painless loss of monocular vision; however, TIA may occur with no ocular involvement whatsoever. Other significant neurological signs and symptoms associated with TIA include dysphasia, contralateral hemiparesis, and paresthesia. Temporary paresis most commonly involves the contralateral arm, leg, or both face and arm, or both arm and leg. Numbness typically involves the contralateral hand, foot, face, and contralateral half of the tongue. A TIA will typically last for 15 minutes, but may go for hours.
TIA and AF result from either an embolic, thrombotic, vasospastic, or hematological phenomenon. Thrombus development occurs via cholesterol deposition and atheroma formation within vessel lumens. From this process forms a thrombus, which may cause transient blood flow cessation and symptoms of TIA or AF. Also, inflammatory cell infiltration of the muscular walls of arteries in giant cell arteritis will lead to lumen narrowing and occlusion with resultant TIA or AF. More commonly, however, the thrombus ulcerates and releases particles which lodge within vessels and result in distal ischemia. This produces the signs and symptoms of TIA or AF. Occasionally, cholesterol emboli is seen lodged at a retinal arteriole bifurcation in patients experiencing AF. However, visible retinal emboli are often not observed as their very nature allows for the emboli to break up and move distally. This explains why cholesterol emboli typically result in transient neurologic deficits. Calcific emboli may dislodge from the heart and indicate valve disturbance. This type of emboli is not malleable and more likely to cause a permanent occlusion of the retinal arteriole.
Vasospastic causes of TIA and AF may be due to non-embolic idiopathic arterial narrowing or the possible release of an as-yet-unidentified vasospastic substance. Occasionally, use of exogenous sources such as cocaine may lead to localized vasospasm and TIA and AF.
Hematological causes of TIA and AF result when there are abnormalities in the normal blood constituents. Hematological causes include polycythemia, sickle cell disease, anemia, and hypercoagulable states.
There is significant morbidity and mortality associated with TIA and AF. Patients experiencing uncomplicated AF have an 85 percent likelihood of full recovery while 10 to 15 percent will eventually develop a central retinal artery occlusion. The average untreated annual stroke rate of patients with untreated AF is 2 percent. Refer these patients to a neurologist or internist for carotid artery studies, such as Doppler imaging or magnetic resonance angiography. If there is significant stenosis of the carotid artery, consult a vascular surgeon for possible endarterectomy. However, these patients are typically medicatedwith blood thinners such as aspirin and they do quite well.
Patients experiencing hemispheric TIA are at more risk. The average annual untreated stroke rate in this group is 8 percent. Refer this patient to a neurologist since other neurological areas are involved in the attack. Typically, this patient requires carotid endarterectomy. The patient with hemispheric TIA has a 25 percent mortality rate within one month, 33 percent within six months, and 60 percent within seven years.
Patients who experience either TIA or AF and have retinal emboli visible at ophthalmic exam also have a high rate of mortality. In this group, the mortality rate is 15 percent within one year, 29 percent within three years, and 54 percent within seven years. In this group, cardiac death is more prevalent than stroke and thus these patients must be referred to a cardiologist.
Amaurosis fugax in elderly patients may be the initial sign of giant cell arteritis. In these cases, devastating vision loss from anterior ischemic optic neuropathy likely ensues within several weeks of an episode of AF. These patients need an immediate Westgren ESR, and possible temporal artery biopsy, along with the requisite carotid studies.
Most cases of TIA and AF show no visible evidence at examination. These diagnoses can be made by history. Optimal management involves referral to the appropriate medical specialist.
The number one hematological cause of AF is sickle cell disease.