10.15 Alcohol Abuse: Neurological Disorders Flashcards
Wernicke’s encephalopathy
General
- Thiamine (Vitamin B1) deficiency : Seen in alcoholics as a result of poor diet
- Affects brainstem and mammillary bodies (high energy demands)
- Krebs/Citric Acid Cycle ->Particularly affect cells with high metabolic demand
- Diffuse lesions: Reticular Activating System
- confusion by itself is enough for diagnosis
Brainstem:
- Medulla: Nystagmus
- Pons: Gaze Palsies
- Midbrain: Enlarged pupils, ptosis
- Reticular Formation: Sleepiness
Wernicke’s encephalopathy
Anatomical sites affected
Brainstem + mammillary body:
Medulla
- Damage to the Vestibular System causes nystagmus: Vestibular system maintains eye position, and when there is dysfunction of the system, eyes will drift, resulting in nystagmus (pathological drift of eye)
- Since the vestibular system is crucial for maintaining fixation (keeping objects fixed on the fovea of the eye), damage to vestibular nuclei results in nystagmus. {horizontal or vertical}
Pons
- difficulty moving eyes together (gaze)
- Gaze Palsy - inability to move both eyes horizontally or vertically
Midbrain
- damage to 3rd nerve -> 3rd nerve palsy
- Bilateral Ptosis (Normal 3rd nerve function: elevates eyelids)
- Bilateral enlarged pupils (Normal 3rd nerve function: pupil constriction)
Traditional triad of wernicke’s
- Ophthalmoplegia ( b + c) - Gaze palsy, third nerve palsies
- Ataxia (b) - Damage to brainstem-cerebellar connections
- Confusion (a + b + c) - Damage to reticular activating system
Wernicke’s encephalopathy causes
- Brainstem lesions in alcoholic
- Especially pregnant women, (Easy to forget: pregnancy causes nausea, vomiting and can result in Wernicke’s)
- Iatrogenic: caused by doctors (giving glucose use up thiamine stores)
Central pontine myelinolysis
- Seen in ill alcoholic with low sodium
- Seen with over rapid restoration of sodium
- compress descending motor pathways -> Quadriplegia
- No Horizontal Gaze; only vertical eye movement (gaze centre in pons damaged)
Anterior lobe of cerebellum syndrome
General
Manifestations
- Damage to representation of the legs within the cerebellum (legs at top, arms at bottom)
Manifestations
- Ataxia of lower limbs/ gait ataxia
- Ataxia of the trunk
- Note: ataxia refers to poor coordination and decomposition (breaking down of the normal sequence) of any voluntary movement*
Wernicke-Korsakoff syndrome; Memory Loss
- Profound anterograde amnesia: Inability to learn new memories.
1st: Wernicke’s encephalopathy
2nd: Korsakoff’s occurs
- Acute confusion, confabulation
- Then, profound cognitive impairment, in this case due to inability to learn new memories.
Confabulation is a memory error defined as the production of fabricated, distorted, or misinterpreted memories about oneself or the world.
- damage to mammillary body
- Patients with lesions to the hippocampus and related structures show severe impairments to new learning
- In the case of Wernicke-Korsakoff, the lesion is in the mammillary body, part of Papez’s circuit.
What is the Papez circuit?
Primary circuit that humans use to lay down new memories
- Amygdala
- Hippocampus
- Parahippocampal gyrus
Types of memory
1. Working memory
- attention
- limited in capacity, focus, duration
2. Long term memory
- Older memories preserved best
- Implicit (learning to ride a bicycle)
- Explicit (what we are doing now..)
3. Semantic
- Colour names
- Sounds of letters
- Capitals of countries
- Knowing what a dog is
- Knowing what Wernicke-Korsakoff syndrome is.
- Language
Alcohol, liver disease & CNS
Liver failure
- Asterixis ( a form of myoclonus, typical of all organ failures)
- An example of an encephalopathy, aka delirium
- can produce coma
Liver disease
- Reduced coagulation factors
- THEREFORE, bleed easier
- THEREFORE, more subdural hematomas (and alcoholics also fall more)
Affect of alcohol on peripheral nervous system
Lower Motor Neuron
- Anterior Horn Cell: No
- Nerve: Yes: peripheral neuropathy
- Junction: No
- Muscle: Yes: myopathy
