Introduction

Neurological conditions are not common but they occupy a great deal of time and effort for orthopaedic surgeons. Polio and spina bifida are becoming increasingly rare in the developed world, as is cerebral palsy. Genetic counselling has reduced the incidence of the genetic disorders. In the developing world many of these conditions remain common but simple public health measures should reduce these dramati­cally in the future.

Classification of neurological disorders

Static, e.g. polio          Progressive, e.g. Huntington’s

Sensory, e.g. leprosy    Mixed, e.g.         Motor, e.g. polio
                                    disseminated
                                   sclerosis
Flaccid, e.g. peripheral   Spastic, e.g. Abnormal movements,
nerve section                 disseminated        e.g. Huntington’s
                                      sclerosis

Static versus progressive

From an orthopaedic point of view, neurological disorders are classified into those which are static and those which are progressive. Static disorders can in fact appear progressive. As an adult gets older and heavier, actions that were previously possible become impossible despite the fact that there has been no deterioration in neurological function. Nevertheless, some conditions such as cerebral palsy and polio tend to be static while other conditions, such as Duchenne muscular dystrophy, are progressive and require a different approach.

Sensory versus motor

Sensory loss such as that caused by traumatic nerve lesions, leprosy and multiple sclerosis may create a limb which cannot be protected from injury, but which is also functionless because the patient does not know where the limb is (loss of proprioception). Other conditions, particularly polio, are pure motor loss. Indeed if there is any associated sensory loss a diagnosis other than polio should be considered. In this case disability and deformity will be a result of loss of muscle power not loss of sensation.

Flaccid versus spastic versus abnormal movements

Flaccid paralysis occurs when a peripheral motor nerve is transected or in the early stages after an upper motor neuron lesion. The limb is flail, and ligaments are susceptible to damage, simply because there is no muscle power protecting them. Spastic paralysis is loss of cortical control of muscles despite the fact that they are’ contracted in spasm and hyper­reflexia. The conversion of an upper motor neuron lesion from flaccid paralysis to spastic paralysis some days after the original lesion may raise false hopes in the patient that recov­ery is imminent. Spastic paralysis will lead to contractures and gross deformity if great care is not taken to maintain limb mobility. Abnormal movements are a characteristic of other neurological conditions. In Parkinson’s disease there is a tremor and a repetitive pill-rolling manoeuvre of the thumb and index finger. In athetoid cerebral palsy, the limbs may writhe and wave around in an uncontrollable manner.