Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig disease or Charcot disease is the most common form of motor neuron disease 1,4, resulting in progressive weakness and eventual death.
ALS typically is diagnosed in middle age. There is a recognised male predilection 1. The majority of cases are sporadic although a small proportion of cases are thought to carry an autosomal dominant mutation on chromosome 21.
Both upper and lower motor neurons are affected with decreased motor strength and with wasting of the muscles of the face, limbs and diaphragm. There is progressive loss of motor strength, with preservation of intellectual and sensory function.
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 to the spinal cord is affected with increased T2 signal and volume loss 3.
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 sensitive).
It is important to note that both of these features are present in varying degrees in normal control patients, and as such an appreciation of what is too much is essential if MRI is to be of benefit.
MR spectroscopy 2:
- decreased NAA
- decreased glutamate
- increased choline
- increased myoinositol
Treatment and prognosis
ALS typically progresses to death in 2-6 years, usually from respiratory complications.
Neurodegenerative diseases are legion and their classification just as protean. A useful approach is to divide them according to underlying pathological process, although even using this schema, there is much overlap and thus resulting confusion.
neurodegenerative MRI brain (an approach)
- measurements and ratios
- midbrain to pons area ratio (for PSP)
- Magnetic Resonance Parkinsonism Index (MRPI) (for PSP)
- frontal horn width to intercaudate distance ratio (FH/CC) (for Huntington's disease)
- intercaudate distance to inner table width ratio (CC/IT) (for Huntington's disease)
- scoring systems
- measurements and ratios
- progressive supranuclear palsy (PSP)
fronto-temporal lobar degeneration (FTLD)
- behavioural variant fronto-temporal dementia (bvFTLD)
- language variant fronto-temporal dementia (lvFTLD), (aka primary progressive aphasia (PPA)
- corticobasal degeneration
- typical / classical Alzheimer's disease
- variant (e.g. posterior cortical atrophy)
- cerebral amyloid angiopathy (CAA)
- transthyretine-associated cerebral amyloidoses
- human prion diseases (not always included as neurodegenerative)
- neuronal intranuclear hyaline inclusion disease (NIHID)
- Alzheimer disease
- spinocerebellar ataxias
- Huntington disease
- hereditary spastic paraplegia
- amyotrophic lateral sclerosis (ALS)
- clinically unclassifiable parkinsonism (CUP)
- 1. Khader SM, Greiner FG. Neuroradiology case of the day. Amyotrophic lateral sclerosis. Radiographics. 19 (6): 1696-8. Radiographics (full text) - Pubmed citation
- 2. Chan S, Shungu DC, Douglas-Akinwande A et-al. Motor neuron diseases: comparison of single-voxel proton MR spectroscopy of the motor cortex with MR imaging of the brain. Radiology. 1999;212 (3): 763-9. Radiology (full text) - Pubmed citation
- 3. Cheung G, Gawel MJ, Cooper PW et-al. Amyotrophic lateral sclerosis: correlation of clinical and MR imaging findings. Radiology. 1995;194 (1): 263-70. Radiology (abstract) - Pubmed citation
- 4. Nelles M, Block W, Träber F et-al. Combined 3T diffusion tensor tractography and 1H-MR spectroscopy in motor neuron disease. AJNR Am J Neuroradiol. 2008;29 (9): 1708-14. doi:10.3174/ajnr.A1201 - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Amyotrophic lateral sclerosis (ALS)||✗|
|Lou Gehrig disease||✓|