Ethanol inhibits thiamine transport in GIT and thiamine
phosphorylation
Wernicke encephalopathy to Korsakoff syndrome:
If untreated, delirium clears up within a month with residual
amnesia in 85% of cases
Neurobiological correlations: damage of anterior
thalami and mamillary bodies (memory), as well as cerebellar
degeneration (ataxia)
Wernicke encephalopathy
Clinical manifestations: acute onset of confusion
(80%), horizontal nystagmus or ophthalmoplegia (30%) and ataxia
(20-25%). Less than 20% present with complete triad.
Diagnosis: Caine criteria requires two of (cause or
any symptom)
Investigations: thiamine blood tests do not
correlate clinically and take time. Treat empirically.
Management
Thiamine replacement prior to glucose replacement
500mg IM/IV TDS for 5 days then 300mg PO TDS for 2 weeks then 100mg
PO daily [eTG]
Thiamine is considered a necessary cofactor for glucose replacement.
Some evidence suggests that the order of replacement does not matter.
Acute glucose replacement (not prolonged) may be relatively safe.
Correct magnesium (required as thiamine cofactor), potassium and
phosphate (refeeding syndrome)
Prognosis: acute and reversible with thiamine
Korsakoff syndrome aka alcohol amnestic disorder
Clinical manifestations: insidious onset of
confabulation, retrograde and anterograde amnesia. Frontal lobe changes
including apathy, avolition, change in personality.
Ribot’s law: newer memories are lost first
Management: thiamine prevents further progression,
likely requires institutionalisation. Memory rehabilitation may assist
with procedural memory (less impaired than declarative memory)
Prognosis: complete resolution in 20% of patients,
irreversible in 25% of patients
Beriberi: severe and chronic form of thiamine
deficiency. WK syndrome is a form of dry beriberi. Rare in first-world
nations.
References: Kaplan’s Synopsis, eTG
Confabulation
Definition: umbrella term in regards to memory
falsification in association with organically derived amnesia whilst in
clear consciousness
Cause: faulty impairment of retrieval of memories
with wrong cue-memory associations and search strategies
Features
Most apparent in autobiographical memory
Patients have no insight. Nil attempt to correct contradictory
statements. Will act on false memories.
Confabulation diminishes as memory impairment worsens
Phenomenology types:
Provoked / embarrassment: patient attempts to cover up memory gaps
with false memories thus revealing social awareness. Patients may recall
reality memories displaced in time. More common type.
Spontaneous / fantastical: frontal lobe impairment with non-elicited
announcements. More rare type. Patients may incorrectly classify
previous fantastical memories as reality memories.