Subacute combined degeneration of cord

- a.k.a Lichtheim disease
- due to vitamin B12 (cobalamin) deficiency, usually associated with pernicious anemia
- associated with chronic nitrous oxide exposure (interfere with methionine synthetase)
- causes classic combination of slowly evolving spastic paraparesis (long tract sign), peripheral neuropathy (absent ankle jerk) and posterior column cord damage (loss of vibration sense and propioception)
- presents with weakness of legs, arms, trunk, tingling and numbness, memory problems, decreased visual acuity (optic neuritis)
- serum B12 less than 100pg/ml and increased level of methyl malonic acid and homocysteine
- MRI: increased T2-weighted signal in posterior column



Differential diagnosis of absent ankle jerk (LMN lesion) + extensor plantar (UMN lesion)
- subacute combined degeneration of cord
- motor neurone disease
- tabes dorsalis (syphilis)
- Friedriech's ataxia
- lesion of cauda equina
- diabetes with CVA
- anterior spinal artery thrombosis affects corticospinal tracts and spinothalamic tracts
- cerebrotendinous xanthomatosis (dementia, gait ataxia, loss of vibration sense, cataracts, tendon xanthoma)