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Amyotrophic Lateral SclerosisAli Nasim MDFellow, Neuroradiology Division at UNC
What is ALS?A-myo-trophic = no-muscle-nourishment
Lateral Sclerosis refers to involvement of the lateral corticospinal tracts.
ALS is a degeneration of somatic motor neurons extending from upper motor cortical pyramidal neurons to lower motor neurons of the brainstem and cord.
History of ALS 1869 - First described in publication by Dr. Jean-Martin Charcot, in Paris.
1881 - Lectures translated into English
ALS: Clinical FindingsSymptoms:
Upper motor - Babinski, spasticity, hyperreflexia.
Lower motor - asymmetric muscle weakness, atrophy, fasciculations
Bulbar signs - dysphagia, slurred speech
ALS: Clinical FindingsTypes:
Classic - UMN and LMN
Only UMN or only LMN
Predominantly bulbar form - worse prognosis
Familial - 15-20%
5600 cases per year in the US, 40-70 y/o, M:F 2:1
ALS: Clinical Findings Progresses distal to proximal, with complete disability within 10 yrs
20% of patients survive >5 yrs
Familial and juvenile onset survive 20-30 yrs after diagnosis
ALS: Clinical Findings Revised El Escorial World Federation of Neurology criteria:
Evidence of LMN degeneration by clinical, electrophysiological, or neuropathological examination
Evidence of UMN degeneration by clinical examination
Progressive spread of symptoms or signs within a region or to other regions (The body is divided into four regions: cranial, cervical, thoracic and lumbosacral)
Absence of electrophysiological, pathological or neuroimaging evidence of other disease processes.
ALS: Imaging FindingsCan have normal imaging
Focal atrophy in chronic cases
T2/FLAIR hyperintensity extending along the corticospinal tract from corona radiata to the brainstem
Contrast enhancement - ?
Deposition of iron in affected cortex
ALS: Imaging FindingsEarly unilateral (left) ALS involvement in a patient with associated callosal agenesis.
ALS: Imaging FindingsCurved MPR: Corticospinal Tract extension
ALS: Imaging FindingsEnhancement is atypical but occasionally seen.
ALS: Imaging FindingsBilateral high T2 signal in corticospinal tracts.
ALS: Imaging FindingsIncreased iron (low T2 signal) deposition in the gray matter of the peri-Rolandic regions which underlying high signal in the white matte and dilatation of the adjacent cortical sulci.
ALS: Imaging FindingsFLAIR images shows high signal in the cortico-spinal tracts due to Wallerian degeneration.
ALS: Imaging FindingsMR Spectroscopy:
Decreased NAA/Cr ratio
Increased choline and myoinositol
Decreased glutamate in the precentral gyrus and peri-rolandi white matter
ALS: Pathology Loss of cortical pyramidal motor neurons and gliosis
Corticospinal tracts with variable patterns of degeneration
Precentral gyrus atrophy
ALS: Pathophyiology Cause of Spontaneous ALS unknown
Single gene mutations can lead to selective motor neuron loss
Glutamate excitotoxicity (etiology unknown)
ALS: Pathophyiology
Familial ALS:
Copper/Zinc Superoxide dismutase (SOD1)gene mutation found to be associated with 20% of familial ALS
Gain of function mutation
ALS: Interesting Info Reports of populations with increased incidence, most notably the Chamarro people of Guam (ALS-PCD)
Incidence ranging 140-400 cases / 100,000 (nml 0.5-2 cases/ 100,00)
Recent theory is that this was due to bat consumption and exposure to BMMA excitotoxins.
ALS: Notable People AffectedLou Gehrig Stephen Hawking Jon Stone
ALS: TreatmentRiluzole - glutamate release inhibitor
-Has been shown to increase NAA/Cr ratio
Symptom treatment - ventilation, anti-spastic medications
References Kalra, S. et al, Neuroimaging in Amyotrophic Lateral Sclerosis. ALS and Other Motor Neuron Disorders. 2003:4 243-248.
Kalra, S. et al, Gabapentin Therapy for Amyotrophic Lateral Sclerosis: Lack of Improvement in Neuronal Integrity Shown by MR Spectroscopy AJNR, Mar 2003; 24: 476 - 480.
Bowen, B. , MR Imaging and Localized Proton Spectroscopy of the Precentral Gyrus in Amyotrophic Lateral Sclerosis AJNR, Apr 2000; 21: 647 - 658.
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