if anyone wants to have a look into detailed things that can cause neuropathy, here is a site which i think is really fantastic. at first (back in feb) i thought it had the best descriptor of b12 deficiency. but now (hit it on a diff search today) i realize it has fantastic information for a great range of things including neurotoxins and channel toxins. here's the path i've been on so far and i'm enthralled:
vitamin syndromes:
http://www.neuro.wustl.edu/neuromuscular/nother/vitamin.htm
sample info:
Thiamine (B1) deficiency (beri-beri)
Biochemistry
Metabolically active form
Thiamine pyrophosphate (TPP): Hydroxyl group is replaced by diphosphate ester group
TPP is a coenzyme for two types of enzymes: Cleave a C-C bond adjacent to a carbonyl group
α-Ketoacid dehydrogenases
Transketolases
TPP dependent enzymes also require a divalent cation, commonly Mg++
Enzyme systems
α-ketoglutarate dehydrogenase: Krebs cycle
Pyruvate dehydrogenase: Pyruvate ® Acetyl CoA
Transketolase: Pentose monophosphate shunt
Sources: Yeast, Pork, Legumes, Cereal grains, Rice (Whole grain)
Clinical features
Extraocular movement paresis
Peripheral neuropathy10
Onset
Progression: Variable; Acute (< 1 month) 50%; Chronic (> 1 year) 20%
Weakness (Legs): 50%
Sensory loss (Legs): 50%
Distribution: Symmetric; Legs > Arms
Weakness
Distal > Proximal
Legs (Foot dorsiflexors) & Hands (Wrist extensors; 80%)
Sensory loss: Large & Small fiber modalities
Pain
Burning feet; Lancinating pain; Calf tenderness
Frequency: Some patients
Autonomic neuropathy: With severe disease
Orthostatic hypotension
Bladder: Flaccid
GI: Gas retention
Tendon reflexes: Reduced or Absent
Cranial nerve weakness (Occasional): Laryngeal (Hoarseness), Face & Tongue
Cerebellar degeneration
Encephalopathy
Acute: Wernicke's disease
Mental status change: Confusion; Memory loss; Agitation
Ataxia: Especially truncal
Ocular: Paresis; Nystagmus; Retinal hemorrhages
Chronic: Korsakoff's psychosis
Memory disorders
Dementia
Systemic
Cardiac failure (Wet beri-beri): Congestive; Tachycardia; Edema
Infantile: Acute cardiac failure
Anorexia: Weight loss
Associated or causative disorders
Alcoholism
Malnutrition: Polished rice; HIV infection; Systemic malignancy; Anorexia nervosa
Dialysis
Malabsorption & repeated vomiting: Gastric resection; Pregnancy
Diet with thiaminases: Raw fish (carp)
Infantile beri-beri: Breast-feeding infants whose mothers are thiamine deficient
Diagnosis
Transketolase activity: Whole blood or Erythrocyte
Increased RBC Transketolase activity after addition of thiamine diphosphate (TPP)
Urine thiamine excretion: 24 hour
Other lab
Serum pyruvate: High
Nerve conduction: Motor & Sensory axon loss
Pathology
Axonal loss: Especially large axons
Subperineurial edema
No segmental demyelination
Treatment
Thiamine
Acute
Immediate: 100 mg/ml solution; Give 100 mg iv before glucose
Follow-up: 100 mg i.m. for 3 to 5 days
Chronic therapy: 50 mg i.m. for 2 weeks, then, Thiamine 50 mg p.o. per day
Prophylactic: Treat with thiamine before giving i.v. glucose
Response: Oculomotor change best; Dementia & Neuropathy less well
External link: GSU
Toxins:
http://www.neuro.wustl.edu/neuromuscular/nother/toxic.htm
sample info:
Nitrous oxide (N2O)
Uses: Dental anesthetic
Neuropathy
Pansensory
Motor: Related to neuropathy or myelopathy
Distal
Pathology: Axonal loss
Myelopathy
Source: Gas used in general anesthesia & Dental analgesia
Some patients with associated cobalamin deficiency
Syndromes: Myelopathy or Polyneuropathy
Onset: Delayed; 3 months to 5 years after exposure
Prognosis: Slow, often incomplete recovery
Optic neuropathy
Megaloblastic anemia
Mechanisms: ? Toxicity related to
Inhibition of methionine synthetase in vitamin B12 related pathways
Association: Sickle cell disease
also interesting info on various channels eg potassium, toxins, etc:
http://www.neuro.wustl.edu/neuromuscular/mother/chan.html
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