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Chapter: Medicine Study Notes : Neuro-sensory

Coma and Stupor

Doll‟s Eye: do eyes remain fixed on target when head is turned. Tests inputs from the neck muscles. Requires linking via medial longitudinal fasiculus of nerves 3, 4, and 6 on both sides

Coma and Stupor

 

·        Checking eyes:

 

o   Doll‟s Eye: do eyes remain fixed on target when head is turned. Tests inputs from the neck muscles. Requires linking via medial longitudinal fasiculus of nerves 3, 4, and 6 on both sides

 

o   Vestibulo-Ocular reflexes: caloric response. 1 ml of ice water evokes nystagmus beating to the opposite side in a normal person. If unconscious, see only deviation without corrective nystagmus

 

o   In deepening diffuse coma without structural damage, the Dolls eye disappears, then the Caloric response. If pupils still reactive then no coning

 

Due to Structural damage

 

·        Only if affecting brain areas required to maintain consciousness: usually infarct, bleed or inflammation

 

·        Reticular Activating System: periventricular grey matter from mid pons up, including the hypothalamus and deep grey matter of both hemispheres

 

·        Most supra-tentorial lesions produce coma due to oedema ® compression of deep hemispheric structures (paramedian diencephalon)

 

·        Features of coning:


·        Transtentorial: progressive drowsiness followed by pupil changes

o   If unilateral cerebral swelling then stretching of ipsilateral 3rd nerve ® ¯parasympathetic innervation

 

o   If diffuse bilateral swelling involving brain stem then impairment of both sympathetic and parasympathetic ® mid position, irregular pupils

·        Posterior fossa coning: headache, stiff neck, ­BP, ¯pulse

 

Due to Diffuse depression of brain function

 

·        Usually metabolic encephalopathy

·        Key differential from structural damage: Pupillary reflexes retained

·        Features: clouded consciousness, difficulty concentrating, altered sleep wake patterns

·        Two basic types:

o  Delirium or acute toxic psychosis: agitated, hallucinatory, severely disorientated

o  Acute confusional state: quieter than delirium

 

·        Immediate evaluation: Glucose, thiamine, Na, Ca, Creatinine, pH, PO2, PCO2, lumbar puncture, sepsis (septicaemia, lung, urinary tract, meningitis)

 

·         Later: LFT, Sedatives, Blood and CSF culture, Electrolytes and Mg, Coagulation, EEG (absence status)


·        Outcome:

o  Sedative drug poisoning: equivalent to GA and will recover with treatment

 

o  Other medical causes: depends on cause, severity and extent. Only 15% make a good recovery if in coma for more than a few hours

 

o  Traumatic: better outlook, related to age, 50% die (many instantly), if ophthalmologic signs of brain stem dysfunction then 90% die or remain vegetative

 

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