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subacute combined degeneration of spinal cord; Lichtheim's disease; Putnam-Dana Syndrome
Etiology:
1) associated with vitamin B12 deficiency
- NOT mitigated by folate supplementation
2) also associated with
a) copper deficiency
b) nitrous oxide exposure
Epidemiology:
- 80% of cobalamin-deficient patients with peripheral neuropathy
Pathology:
1) degeneration of dorsal, anterolateral, lateral columns of spinal cord
a) demyelination early
b) Wallerian degeneration in later stages
c) mid thoracic segments of the spinal cord affected most
2) occasionally foci of perivascular demyelination in cerebral white matter
- large ascending & descending tracts in internal capsule, the cerebellar peduncles & the pons tend to be spared
3) astrocytosis & neuroglial scarring may occur
Clinical manifestations:
1) stage 1
a) paresthesias occur early; may preceed other abnormalities by months
b) gait ataxia may progess over a few weeks to over 1 year
c) spastic paraparesis
d) lower limbs generally affected before upper limbs
e) writing impairment may occur
2) stage 2
a) severe ataxic paraplegia
b) anesthesia of the legs & trunk
c) may develop rapidly
3) stage 3
a) complete paraplegia
b) total anesthesia
4) may be associated with mental status changes (4-28%)
a) depression
b) confusion
c) amnesia (Wernicke's syndrome)
d) dementia
e) paranoid psychosis
Laboratory:
- cerebrospinal fluid analysis
a) slightly increased protein
b) CSF vitamin B12 levels much less than serum levels
- serum chemistries consistent with vitamin B12 deficiency
- vitamin B12 in serum is low
- serum methylmalonic acid is high
- serum homocysteine is high
- complete blood count (CBC) consistent with macrocytic anemia
- MCV is high
- hemoglobin in blood is low
- peripheral smear consistent with vitamin B12 deficiency
- hypersegmented neutrophils & macrocytes
Radiology:
-> MRI of the cervical & thoracic spinal cord may show demyelination
a) in mid-thoracic region, zone of demyelination may extend around the spinal cord
b) in cervical region, posterior columns alone may show demyelination
Complications:
-> demyelination of the optic nerves has been described
Management:
- vitamin B12 replacement
- may halt progression of disease but generally does not reverse existing pathology [2]
- see vitamin B12 deficiency
Related
lateral column
posterior (dorsal) column
vitamin B12 deficiency
General
neurodegenerative disease
spinal cord disease; myelopathy (disease/disorder primarily affecting spinal cord)
References
- Greenfield's Neuropathology, 5th ed, Adams JH & Duchen LW (eds),
Oxford University Press, New York, 1992, pg 828
- Medical Knowledge Self Assessment Program (MKSAP) 17, 18.
American College of Physicians, Philadelphia 2015, 2018.