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Clinical Findings
A. Symptoms and Signs:
Difficulty in swallowing, chewing, coughing, breathing, and talking (dysarthria) occur with bulbar
involvement. In progressive bulbar palsy, there is drooping of the palate, a depressed gag
reflex, pooling of saliva in the pharynx, a weak cough, and a wasted, fasciculating tongue. In
pseudobulbar palsy, the tongue is contracted and spastic and cannot be moved rapidly from side to
side. Limb involvement is characterized by motor disturbances (weakness, stiffness, wasting,
fasciculations) reflecting lower or upper motor neuron dysfunction; there are no objective changes
on sensory examination, though there may be vague sensory complaints. The sphincters are
generally spared. The disorder is progressive
and usually fatal within 3–5 years; death usually results from pulmonary infections. Patients
with bulbar involvement generally have the poorest prognosis...
B. Laboratory and Other
Studies: Electromyography may show changes of chronic partial denervation, with abnormal
spontaneous activity in the resting muscle and a reduction in the number of motor units under
voluntary control. In patients with suspected spinal muscular atrophy or amyotrophic lateral
sclerosis, the diagnosis should not be made with confidence unless such changes are found in at
least three extremities. Motor conduction velocity is usually normal but may be slightly reduced,
and sensory conduction studies are also normal. Biopsy of a wasted muscle shows the histologic
changes of denervation. The serum creatine kinase may be slightly elevated but never reaches the
extremely high values seen in some of the muscular dystrophies. The cerebrospinal fluid is
normal. A familial form of amyotrophic
lateral sclerosis has been described with autosomal dominant inheritance, related to
mutations in the copper-zinc superoxide dismutase gene on the long arm of chromosome 21. X-linked
bulbospinal neuronopathy is associated with an expanded trinucleotide repeat sequence on the
androgen receptor gene and carries a more benign prognosis than other forms of motor neuron disease.
There have been recent reports of juvenile spinal muscular atrophy due to hexosaminidase
deficiency, with abnormal findings on rectal biopsy and reduced hexosaminidase A in serum and
leukocytes. Pure motor syndromes resembling motor neuron disease may also occur in
association with monoclonal gammopathy or multifocal motor neuropathies with conduction
block. A motor neuronopathy may also develop in Hodgkin's disease and has a relatively
benign prognosis..
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