Motor neuron disease: Treatment, symptoms, advice and help
About motor neuron disease
This is a progressive disorder of unknown causes, in which there is degeneration of motor neurons in the spinal cord and cranial nerve nuclei, and of pyramidal neurons in the motor cortex.
Motor neuron disease; Incidence, age and sex
The prevalence of the disease is about 5/100, 000. The condition usually begins after the age of 50 years and is very uncommon before the age of 30 years. It affects males more commonly than females.
Signs & symptoms of motor neuron disease: Diagnosis
The disease begins with limb muscle weakness, cramps and disturbance of speech / swallowing (dysathria / dysphagia). On examination there is wasting and fasciculation of muscles, weakness muscles of limb, tongue, face and palate, spasticity, exaggerated tendon reflexes and extensor plantar responses. The external ocular muscles and sphincters usually remain intact. There is no objective sensory deficit and no intellectual impairment, in most cases.
Course: The symptoms often begin focally in one part and spread gradually but relentlessly to become widespread.
Electromyography helps to confirm the presence of fasciculation and denervation, and is particularly helpful when pyramidal features predominate. Sensory nerve conduction and motor conduction studies are normal. Spinal imaging and brain scanning may be necessary to exclude focal spinal or cerebral disease. CSF examination is usually normal, though a slight elevation in protein concentration may be found.
Causes and prevention of motor neuron disease
Between 5 and 10% of cases are familial, and in 20% of such families, the disease is caused by a mutation in the superoxide dismutase (SODI) gene. For the remaining 95%, possible causes include viral infection, trauma, exposure to toxins and electric shock, but no sound evidence exists to support any of these.
Motor neuron disease: Complications
Motor neuron disease is relentlessly progressive; the mean time from diagnosis to death is 1 year, with most patients dying within 3-5 years of the onset of symptoms. Death is usually from respiratory infection and failure and the complications of immobility.
Motor neuron disease: Treatment
Riluzole, 100mg per day appears to be modestly effective in prolonging survival for patients with motor neuron disease by about 2 months. However, the economics of its use have yet to be fully assessed.
Psychological and physical support, with help from occupational and speech therapists and physiotherapists, is essential to maintain the patient’s quality of life. Mechanical aids such as splints and walkers reduce handicap. Feeding by percutaneous gastrostomy may be necessary because of bulbar failure. Non-invasive ventilatory support has been shown to improve the quality of life by alleviating symptoms from weak respiratory muscles and has a small effect on prolonging life. Relief of distress in the terminal stages usually requires the use of opiates and sedative drugs.