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Medicine 5th year, 6th lecture/part two (Dr. Mohammed Tahir)

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The lecture has been given on May 26th, 2011 by Dr. Mohammed Tahir.

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Medicine 5th year, 6th lecture/part two (Dr. Mohammed Tahir)

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

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