wernicke's encephalopathy

Question 1

definition

Answer 1

Wernicke’s encephalopathy is a neurological emergency resulting from thiamine deficiency with varied neurocognitive manifestations, typically involving mental status changes and gait and oculomotor dysfunction.

Question 2

pathophysiology

Answer 2

Thiamine deficiency leads to decreased activity of thiamine-dependent enzymes. This triggers a sequence of metabolic events resulting in energy compromise and ultimately neuronal death in certain neuronal populations with high metabolic requirements and high thiamine turnover.[11] The areas commonly affected include the medial dorsal thalamic nucleus, mammillary bodies, the periaqueductal grey matter, and the floor of the fourth ventricle, which includes the ocular motor and vestibular nuclei and the cerebellar vermis.[4] Lesions may also involve the fornices, the hippocampus, the area round the third ventricle, the quadrigeminal bodies, and the cortex. The predilection to affect memory circuits is responsible for the most important sequela of Wernicke’s encephalopathy - Korsakoff’s psychosis

Question 3

signs and symptoms

Answer 3

classically presents as a triad – confusion, ataxia, opthalmoplegia (but only this combination in 10% of patients)

• mental slowing, impaired concentration, apathy
• occulomotor findings – gaze palsies, 6th nerve palsy, impaired vestibulo-occular reflexes
• delirium, psychosis, confusion
• gait dysfunction
• papilloedema, retinal haemmorhage
• tachycardia or hypotension
• mild irritability
• hearing loss
• seizures
• spastic paraparesis

Question 4

risk factors

Answer 4

• prolonged vomiting or diarrhoea
• AIDS
• history of GI surgery
• bariatric surgery
• alcohol dependence or illegal drug use
• cancer and chemotherapy (due to increased vomiting and/or reduced food consumption. Ifosfamide may also interfere with the conversion of thiamine to its active metabolite (thiamine pyrophosphate) or compete with it to cause a functional deficiency mimicking Wernicke’s encephalopathy.)
• malnutrition

Question 5

investigations

Answer 5

1st investigations:

• therapeutic trial of parenteral thiamine
• finger prick glucose
• FBC (An infection may trigger acute decompensation of thiamine deficiency.)
• serum electrolytes
• renal function
• LFTs
• urinary and serum tox screen
• serum ammonia (A metabolic encephalopathy due to hyperammonaemia can easily mimic or be confused with Wernicke’s encephalopathy.)
• blood alcohol level
• blood thiamine + thiamine metabolites
• serum magenesium (Magnesium deficiency is common in persons who misuse alcohol on a chronic basis. Magnesium deficiency may impair the therapeutic benefit of thiamine, because magnesium serves as a co-factor in enzymes that need thiamine pyrophosphate.)

others to consider:

• LP (excluding meningitis, encephalitis, and subarachnoid haemorrhage, which may present with similar findings.)
• CT and MRI brain