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In some spinal cord disorders, there in selected loss of the anterior horn cell
in the ventral gray matter. Infection with the poliomyelitis virus, now rare,
shows a predilection for the anterior horn cells and produces asymmetric lower
motor neuron involvement and a cerebrospinal fluid pleocytosis after a
febrile illness. Some cases of a poliomyelitis-like syndrome have recently been
reported in West Nile encephalitis.
In addition to infection, selective anterior horn cell damage occurs in some
inherited conditions, known as spinal muscular atrophy. Spinal muscular atrophy
type I (Werdnig-Hoffmann disease) is a pure anterior horn cell degeneration
presenting in infancy, though more slowly progressive forms are recognized in
older children and some adults.
Lastly, is the important disorder, amyotrophic lateral sclerosis (ALS) in
which there is a progression of both lower (anterior horn cell) and upper
(corticospinal tract) motor neuron signs. Patients develop atrophy, weakness,
fasciculations, and spasticity along with hyperreflexia and
Babinksi signs (see
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