Spinal infection

  Spinal column infection

Spinal column infection is not common and 30 per cent of cases have a significant delay in diagnosis, the average being 3 months. The common presenting symptoms are fever and unremitting pain especially at night. The distribution is bimodal, occurring in the very young and the very old. In children the infection is frequently sterile and may simply be a discitis. Very young children may present simply with malaise and inability to walk. There may be a scoliosis. The infection is usually centred on the disc, and in the early stages there may be no X-ray changes although MRI will show the typical changes of oedema in the end plates and disc, with changes in the surrounding soft tissues. After 2 weeks narrowing of the disc space usually occurs. Needle biopsy of the disc only grows bacteria in about 40 per cent of cases. Unless the child is septicaemic, expectant treatment can be tried. Established infection or failure to improve requires treatment with broad-spectrum antibiotics. A plaster jacket may be helpful in controlling pain and accelerating resolution of symptoms. In the long term the disc may reconstitute, or occasionally spontaneous fusion of the disc may occur.

Infection of the spinal column is usually more serious in adults. As in children it is usually centred on the disc, and by the time of presentation X-ray changes are usually present in the form of disc space narrowing with destruction of the end plates. The patient may be generally unwell and septicaemic. Many patients have reduced immunity to infection due to conditions such as diabetes or carcinoma, and recent urinary catheterisation or surgery is not uncommon. It is important to establish the bacterium causing the infection if possible before starting treatment. The most common bacterium is Staphylococcus aureus, but almost any bacterium can cause the infection and tuberculosis must always be considered as a possibility (see below). Blood cultures should always be carried out and in many cases this will establish the type of bacteria. Needle biopsy of the disc space is an alternative method of diagnosis. This is done under local anaesthetic with X-ray control, and will confirm the diagnosis in about 60 per cent of cases. Surgery tends to be used for patients where there is considerable bone destruction or deformity,. neurological compromise due to compression on the spinal cord or failure to eradicate the infection with antibiotics. Simple stabilisation of the infected area combined with antibiotics may be adequate in older individuals, but otherwise débridement of the disc space, bone grafting and stabilisation are most likely to result in cure. Surprisingly internal fixation in these patients rarely seems to cause problems of persistent infection, although it may be advisable to remove the fixation once the bone has healed. Antibiotic treatment is usually continued for some months.

Some cases of disc space infection will progress to epidural abscess. This will present with neurological symptoms and signs and should be drained as a surgical emergency (see below).

 

Tuberculosis

Tuberculosis is more frequently seen in the Third World than in the developed world but it is becoming more common, and should always be considered as a possible diagnosis in those with spinal infection.

Treatment with multiple antibiotics over long periods has proven very effective in treating spinal tuberculosis, and has been shown to be effective in managing some patients with paraplegia. Eventual fusion of the infected area can be expected in around 80 per cent of patients without surgery. Surgery combined with antibiotics is used where there is a large abscess which requires draining or considerable deformity of the spine. Failure of antibiotic treatment may also be a surgical indication. In general the best surgical results are with anterior débridement and bone grafting of the infected area.

Spinal epidural abscess

Infection within the epidural space is a rare but potentially disastrous condition. Usually due to haematogenous spread from remote sites or associated with intravenous drug usage, pus can collect and spread within the epidural space and cause compression of the spinal cord or cauda equina. Infection may spread from local sites (discitis/vertebral osteomyelitis or paravertebral infection) (see Fig. 33.33) and may present as a postoperative complication.

Staphylococcus aureus represents the commonest causative organism. A variety of other organisms including bacteroides, aerobic and anaerobic streptococci may be found. Consider unusual organisms in association with immune compromise, including fungal infections.

Presentation

Presentation includes:

severe local pain;

systemic signs of infection;

radicular signs;

onset of symptoms and signs of cord and cauda equina compression.

Progression of symptoms can be very rapid and therefore early recognition is vital to allow a good outcome. A high index of suspicion to achieve diagnosis before the onset of complete paralysis is very important. If the diagnosis is delay­ed to this point, vascular thrombosis may result in irreversible paralysis.

Diagnosis

Diagnosis includes:

clinical awareness of the condition;

general tests: haemoglobin, white cell count, ESR, CRP, blood cultures, midstream urine;

plain spinal X-rays, chest X-ray;

MRI scan.

Plain X-rays may show evidence of osteomyelitis and should be performed, but MRI is the investigation of choice (see Fig. 33.34). The precise location of the abscess and its extent and position in relation to the cord can all be identified. If suspected the investigation must he carried out as an emergency.

In the absence of MRI, myelography and CT myelography would enable the diagnosis of an epidural mass, but it is harder to define the full extent of the lesion. Care must be taken to avoid carrying infection into the intradural compartment at the time of lumbar puncture. If a cervical abscess is suspected, a lumbar spinal puncture can be used, the contrast being run up to the cervical region. However, if the abscess is thought to be in the thoracolumhar region, a cervical puncture must be made. CT rnyelography will help to define the extent of the lesion and will also provide important anatomical information about adjacent vertebral bodies. CSF examination shows a mild leucocytosis with elevation of the neutrophil or lymphocyte counts. Protein levels will be increased.  

Management

Management of this condition includes:

  surgical drainage of the abscess;

  antibiotic therapy;

  treatment of source of infection/paravertebral infection;

  management of neurological disability.

        Patients with an epidural abscess showing signs of severe systemic infection require full supportive therapy. Drainage of the pus via a posterior or anterior approach should he carried out as an emergency once a diagnosis is suspected. For anteriorly placed lesions, usually in the cervical region, an anterior cervical discectomy with opening of the posterior longitudinal ligament reveals the pus. Samples should he sent for microscopy and Gram stain, set up for culture and antibiotics started. Avoid instrumentation or insertion of bone grafts.

          Dorsally placed collections can be drained via a laminectomy.

         If available, the advice of a hone infection unit should be taken. Certainly, advice from a medical microbiologist will help in the choice of antibiotic and the duration of treatment. In principle, intravenous therapy via a long intravenous line, and modified according to culture results, should be continued for at least 2 weeks. Be prepared to repeat the MRI scans to ensure that the abscess has been fully drained.

Any residual neurological deficit will require input from physiotherapists and occupational therapists, directed by a rehabilitation facility. Recovery, however, may he slow and protracted over many months. Finally, any other site of infection should he dealt with as indicated.