Amyotrophic lateral sclerosis
Also known as Lou Gehrig's
disease (after the famous baseball player), ALS is the most common
form of progressive motor neuron disease. The incidence is 1:100,000 prevalence
4-6:100,000. It appears mainly in advancing age and male slightly more than
In each of these diseases, the affected motor neurons undergo
shrinkage, often with accumulation of the pigmented lipid (lipofuscin) that
normally develops in these cells with advancing age. In ALS, the motor neuron
cytoskeleton is typically affected early in the illness. Focal enlargements
are frequent in proximal motor axons; ultrastructurally, these "spheroids"
are composed of accumulations of neurofilaments.
Both upper and lower motor neuron abnormalities are found.
Mixture of both upper and lower motor neuron abnormali?ties are found.
Typical patient with ALS develops progressive limb weakness affecting
distal more than proximal areas, and especially affecting the small muscles
of the hand. Early atrophy and fasciculations are prominent.
The deep tendon reflexes are usually preserved in the early phase of
the disease, at least in the upper extremities. Signs of upper motor neuron
involvement may develop at any time but almost always appear by the time
muscle involvement has lasted a year. Characteristically bladder and bowel
functions remain unaffected. ALS spares the extraocular muscles but in the
late stages can interfere with supranuclear oculomotor control.
Amyotrophic lateral sclerosis may be associated with a form of late-life
dementia characterized by prominent signs of frontal lobe dysfunction.
It progresses over 2 to 7 years until death.
Mixture of LMND with exaggerated reflexes. Painless weakness and atrophy
of the hands, fasciculations in the entire upper extremities, and spasticity
and reflex hyperactivity of the legs with extensor plantar responses.
CSF is normal. Electrodiagnostic testing is helpful.
Average survival is 3yrs. Death from pulmonary insufficiency and infection
N.B. Progressive bulbar palsy: a variant of ALS that causes relatively
rapidly advancing upper and lower motor neuron involvement of the muscles
of the jaw, pharynx, and tongue.
There is no treatment capable of arresting the underlying pathologic
process in ALS. The drug riluzole was approved for use in ALS because it
produces a modest lengthening of survival. In one trial, the survival rate
at 18 months with riluzole (100 mg/d) was similar to placebo at 15 months.
The mechanism of this effect is not known with certainty; it may reduce
excitotoxicity by diminishing glutamate release.
In the absence of a primary therapy for ALS, a variety of rehabilitative
aids may substantially assist ALS patients.