medicine.Coma.(dr.muhamad tahir)
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medicine.Coma.(dr.muhamad tahir) medicine.Coma.(dr.muhamad tahir) Presentation Transcript

  • Evaluation of Patients inComa
  • Definitions„ Coma: “Unarousable unresponsiveness in which the subjects lie with eyes closed”
  • Consciousness„ Two components of conscious behavior ƒ content- the sum of cognitive and affective function ƒ arousal- appearance of wakefulness„ Content depends on arousal but normal arousal does not guarantee normal content
  • Really SimpleNeuroanatomy„ Arousal: where is it localized? ƒ Ascending Reticular Activating System (ARAS) ‘core of the brainstem’ ƒ receives input from numerous somatic afferents ƒ projects to midline thalamic nuclei (which are in a circuit with cortical structures) and the limbic system
  • ARAS„ ARAS acts as a gating system, increasing or decreasing thalamic inhibitory influence on the cortex ƒ alters effect of sensory stimuli ascending ƒ alters descending cortical stimulation
  • Demands of Arousal„ Function of ARAS-Thalamic-Cortical system depends on: ƒ anatomic integrity of structures ƒ metabolic integrity (circulatory integrity) ƒ communicative integrity (neurotransmitter function)
  • Coma Fact Number One„ Coma implies dysfunction of: ƒ ARAS or ƒ Both hemi-cortices„ Anatomically, this means ƒ central brainstem structures (bilaterally) from caudal medulla to rostral midbrain ƒ both hemispheres
  • Clues from History„ Onset of symptoms ƒ sudden onset ƒ fluctuations„ Associated neurologic symptoms„ Medications
  • Breathing„ Abnormalities of respiration can help localize but almost always in the context of other signs ƒ Central-reflex Hyperpnea (midbrain- hypothalamus) ƒ Apneustic, cluster, Ataxic (Lower pons) ƒ Loss of automatic breathing (medulla)
  • Cranial Nerve Exam„ Systematic assessment of brainstem function via reflexes„ Cranial Nerve Exam ƒ Pupillary light response (CN 2-3) ƒ Occulocephalic/calorics (CN 3,4,6,8) ƒ Corneal reflex (CN 5,7) ƒ Gag refelx (CN 9,10)
  • .Pupillary Light Responses„ Afferent Limb: Optic Nerve„ Efferent Limb: Parasympathetics via occulomotor„ Midbrain integrity/ tectum„ Uncal Herniation (3rd nerve dysfunction)„ Pupillary resistance to insult
  • Pupillary Light Responses„ Be aware of drug effects ƒ Systemic and Local„ Avoid ‘PERLA’ ƒ State size, before and after light stimulation ƒ Specify right and left
  • Pupils: Localizing Value„ Pons-pinpoint pupils ƒ Symp. Dysfinction plus parasymp.irritation„ Midbrain-Large fixed pupils unresponsive to light, hippus„ Horner’s- symp.dysfunction„ Unilateral dilation- parasymp. Dysfunction usually due to 3rd nerve lesion
  • Ciliospinal Reflex„ 1-2 mm pupillary dilatation evoked by noxious cutaneous stimulation„ More prominent in sleep or coma than during wakefulness„ Test integrity of symp.pathways in comatose patients„ Not particularly useful in evaluating brainstem function
  • Corneal Reflex„ Afferent: Trigeminal Nerve„ Efferent: Third Nerve (Bell’s Phenomenon and Facial Nerve (Eye closure)„ Tests dorsal midbrain (Bell’s) and pontine integrity (Eye closure)
  • Eye Movements„ Before maneuvers attempted note resting position ƒ Midline ‚ Deviation suggests frontal/pontine damage ƒ Conjugate ‚ Dysconjugance suggests CN abn. ƒ Moving ‚ Roving, dipping, bobbing
  • Occulocephalic/ Calorics„ Same reflex elicited differently„ Afferent: Eighth nerve„ Efferent: 3,4,6 via MLF and PPRF„ Occulocephalics may also involve proprioceptive afferents from the neck
  • Occulcephalic Reflex„ Brisk rotation of head with eyes held open„ Watch for contraversive movements„ Next: ƒ Flexion: eyes deviate up and eyelids open (doll’s head phenomenon) ƒ Extension:eyes deviate downward
  • Caloric reflex„ Ensure TM integrity„ Elevation of head to 30 degrees (so that lateral semicircular canal is vertical)„ Instillation of up to 120 ml of ice water ƒ Awake: deviation toward,nystagmus away ƒ Comatose: deviation toward„ Wait 5 minutes, do other ear
  • Calorics„ Watch for conjugance of deviation„ To test vertical eye movements ƒ Both ears, cold water-downward gaze ƒ Both ears, warm water-upward gaze
  • Gag Reflex„ Afferent: Glossopharyngeal„ Efferent: Vagus„ Taken in context of other findings
  • Motor Exam„ Assess tone, presence of asterixis„ Response to painful stimuli ƒ none ƒ abnormal flexor ƒ abnormal extensor ƒ normal localization/withdrawal„ Avoid use of decerebrate/ decorticate
  • Reflexes„ Brainstem„ Deep tendon ƒ Biceps, brachioradialis, triceps ƒ Patellar, Achilles ƒ Plantar Responses„ Superficial skin ƒ Abdominal, cresmasteric
  • Uncal herniaiton„ Expanding lesions in lateral middle fossa„ Compression of hippocampal gyrus over free edge of tentorium„ Three stages described ƒ Early third nerve ƒ Late third nerve ƒ Midbrain-Upper pons stage
  • Goals in Emergency„ Primary Neurological Process? ƒ evidence of raised ICP ƒ focal findings, especially that implicate brainstem structures„ Secondary Processes ƒ signs of infection, toxic/metabolic processes ƒ relative lack of focality
  • Coma Mimics„ Akinetic mutism„ ‘Locked-in’ syndrome„ Catatonia„ Conversion reactions
  • Akinetic Mutism„ Silent, immobile but alert appearing„ Usually due to lesion in bilateral mesial frontal lobes, bilateral thalamic lesions or lesions in peri-aqueductal grey (brainstem)
  • “Locked-In’ Syndrome„ Infarction of basis pontis (all descending motor fibers to body and face)„ May spare eye-movements„ Often spares eye-opening„ EEG is normal or shows alpha activity
  • Catatonia„ Symptom complex associated with severe psychiatric disease with: ƒ stupor, excitement, mutism, posturing ƒ can also be seen in organic brain diease: encephalitis, toxic and drug-induced psychosis
  • Conversion reactions„ Fairly rare„ Occulocephalics may or may not be present„ The presence of nystagmus with cold water calorics indicates the patient is physiologically awake„ EEG used to confirm normal activity