ANSWER 13
This man has motor neurone disease. This is a degenerative disease of unknown cause
that affects the motor neurones of the spinal cord, the cranial nerve nuclei, and the motor
cortex. The disease usually presents between the ages of 50 and 70 years.
Weakness and wasting of the muscles of one hand or arm is the commonest presentation.
Weakness is most marked after exertion. Painful cramps of the forearm muscles are com-
mon in the early phases of the disease. Patients may present with lower limb weakness or
with dyarthria or dysphagia. The characteristic physical sign of this condition is fascicu-
lation, which is an irregular rapid contraction of segments of muscle, caused by denerva-
tion of the muscle from a lower motor neurone lesion. Reflexes can be brisk due to loss of
cortical motor neurones. There is no sensory loss.
In advanced cases diagnosis is easy, but early cases are more problematic. Limb weakness
worsening with fatigue may be confused with myasthenia gravis. Dysphagia and dysarthria
in the elderly are much more commonly due to the pseudobulbar palsy of cerebrovascular
disease. Cervical myelopathy is another common cause of wasting and fasciculation of the
upper limbs without sensory loss. Brachial plexus lesions from trauma or invasion by an
apical lung tumour (Pancoast tumour) may affect one arm. A predominant motor periph-
eral neuropathy causes a symmetrical pattern of weakness and reflexes are reduced.
Unfortunately motor neurone disease is a progressive and incurable condition. Patients
tend to develop a spastic weakness of the legs. Bulbar palsy causes dysarthria and dys-
phasia. Sphincter function is usually not affected. Intellect is generally not affected.
There is no curative treatment for this condition. The mean duration of survival from
presentation is between 2 and 4 years. The patient and his family will have to be told of
the diagnosis and prognosis. Support must be given by a multidisciplinary team. As the
disease progresses and speech deteriorates communication may be helped by using com-
puters. A feeding gastrostomy may be required to enable adequate calorie intake. Non-
invasive ventilation can be used to help respiratory failure, but death usually occurs from
bronchopneumonia.
- Motor neurone disease most commonly presents with weakness and wasting of the
muscles of one hand. - Fasciculation of the muscles is characteristic of this condition.
- There is no sensory loss in this condition.