Amyotrophic lateral sclerosis

ALS, also known as Lou Gehrig disease is a relentlessly progressive neurological disorder characterised by death of upper motor neurons. It results in decreased motor strength and wasting of the muscles of the face, limbs and diaphragm. It typically progresses to death in 3 - 6 years, usually from respiratory complications.

Imaging

The earliest MR manifestation is hyperintensity on T2WI in the corticospinal tracts, seen earliest in the internal capsule, as the fibers are most concentrated here. Eventually the entire tract from motor strip (Betz cells in the cortex) to the spinal cord (anterior horn cells) is affected (Wallerian degeneration). 

Iron deposition in the cortex is demonstrated as loss of signal most evident on T2* weighted sequences (see Case 2: SWI) - it is seen on T2WI in 40 - 60% (SWI is presumably more sensative).

MRS demonstrates:

• decreased NAA
• decreased glutamate
• increased choline
• increased myoinositol