Amyotrophic Lateral Sclerosis
- Most frequent type of motor neuron disease, with an estimated incidence of 1–2 per 100,000 people
- Affects both the upper and lower motor neurons. Lower motor neuron signs and symptoms include progressive muscle weakness, fasciculation, and atrophy. Upper motor neuron signs and symptoms include hypereflexia and spasticity.
- Key Diagnostic Features: T2 and proton-density (more sensitive) WI demonstrate hyperintensity involving the corticospinal tracts, from the corona radiata to the anterolateral columns of the spinal cord. It should be noted that the corticospinal tracts can normally appear hyperintense on 3T MRI. Frequently, hypointensity is seen along the posterior cortex of the precentral gyrus in ALS patients. This, however, can also be a normal finding reflecting normal iron deposition in elderly patients. Increased iron deposition in the cortex of the precentral gyrus also has been noted to occur in patients with Alzheimer disease. High signal intensity in the corticospinal tracts on T1 magnetization transfer images has shown high sensitivity/specificity in some early diagnosed cases. Spectroscopy (NAA/Cr < 2.0) and diffusion tensor imaging has also been used to diagnose ALS cases.
- DDx: Primary lateral sclerosis; Wallerian degeneration; metabolic, inflammatory, and demyelinating disease conditions
- Rx: None. Dismal prognosis, with death occurring usually within a decade of symptom onset.
