Amyotrophic Lateral Sclerosis
The Common Vein Copyright 2010
Definition
ALS is a neurodegenerative disorder of the CNS that has an undetermined cause, and that is characterized by loss of lower motor neurons in spinal cord and brainstem and upper motor neurons that project in corticospinal tracts. The loss occurs progressively, patients lose motor capacities until eventually respiratory failure and death develops. The famous baseball player Lou Gehrig was affected by this disease, hence its epononym.
Structurally, the anterior roots of the spinal cord are thin, and the precentral gyrus may be atrophic in severe cases.
Functionally, there are signs of UMN and LMN loss, though at an initial stage there can be only UMN / LMN / bulbar or even dyspnea.
Clinically, patients present initially with asymmetric weakness of the hands – dropping objects and inability to carry out fine motor tasks. Complain of pain due to cramping and twitches in extremities. A sign of denervation ? fasciculation ? develops as the disease progresses, and, as mentioned, eventually the respiratory muscles will be affected, so that patients have frequent pulmonary infections.
The diagnosis maybe be achieved clinically, but because the differential diagnosis includes many other diseases, blood tests, electromyography and neuroimaging may be required.
Neuroimaging is important to exclude structural causes, due to masses, inflammation, or infiltrative processes that may cause UMN signs. Proton density-weighted scans, rather than fluid attenuated inversion recovery or T2-weighted fast spin-echo sequences of the brain, may reveal an abnormal signal due to wallerian degeneration within the motor tracts, mostly in the internal capsules.
Treatment is attempted with Riluzole, which works as an glutamate antagonist, decreasing its neurotoxicity and slowing down the degeneration, but an effective treatment is not known to date.
amyotrophic lateral sclerosis: AKA Lou Gehrig’s Disease, an upper and lower motor neuron disease characterized by progressive weakness without sensory deficit