PT - JOURNAL ARTICLE AU - J J Graber AU - F T Sherman AU - H Kaufmann AU - E H Kolodny AU - S Sathe TI - Vitamin B<sub>12</sub>-responsive severe leukoencephalopathy and autonomic dysfunction in a patient with “normal” serum B<sub>12</sub> levels AID - 10.1136/jnnp.2009.178657 DP - 2010 Dec 01 TA - Journal of Neurology, Neurosurgery &amp; Psychiatry PG - 1369--1371 VI - 81 IP - 12 4099 - http://jnnp.bmj.com/content/81/12/1369.short 4100 - http://jnnp.bmj.com/content/81/12/1369.full SO - J Neurol Neurosurg Psychiatry2010 Dec 01; 81 AB - Leukoencephalopathy and autonomic dysfunction have been described in individuals with very low serum B12 levels (&lt;200 pg/ml), in addition to psychiatric changes, neuropathy, dementia and subacute combined degeneration. Elevated homocysteine and methylmalonic acid levels are considered more sensitive and specific for evaluating truly functional B12 deficiency. A previously healthy 62-year-old woman developed depression and cognitive deficits with autonomic dysfunction that progressed over the course of 5 years. The patient had progressive, severe leukoencephalopathy on multiple MRI scans over 5 years. Serum B12 levels ranged from 267 to 447 pg/ml. Homocysteine and methylmalonic acid levels were normal. Testing for antibody to intrinsic factor was positive, consistent with pernicious anaemia. After treatment with intramuscular B12 injections (1000 μg daily for 1 week, weekly for 6 weeks, then monthly), she made a remarkable clinical recovery but remained amnesic for major events of the last 5 years. Repeat MRI showed partial resolution of white matter changes. Serum B12, homocysteine and methylmalonic acid levels are unreliable predictors of B12-responsive neurologic disorders, and should be thoroughly investigated and presumptively treated in patients with unexplained leukoencephalopathy because even long-standing deficits may be reversible.