1. Evaluation of Patients in
Coma

2. Definitions
„ Coma: “Unarousable unresponsiveness in
which the subjects lie with eyes closed”

3. 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

4. Really Simple
Neuroanatomy
„ 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

5. 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

6. 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)

7. 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

8. Clues from History
„ Onset of symptoms
ƒ sudden onset
ƒ fluctuations
„ Associated neurologic symptoms
„ Medications

9. 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)

10. 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)

11. .Pupillary Light Responses
„ Afferent Limb: Optic Nerve
„ Efferent Limb: Parasympathetics via
occulomotor
„ Midbrain integrity/ tectum
„ Uncal Herniation (3rd nerve dysfunction)
„ Pupillary resistance to insult

12. 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

13. 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

14. 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

15. 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)

16. 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

17. 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

18. 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

19. 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

20. 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

21. Gag Reflex
„ Afferent: Glossopharyngeal
„ Efferent: Vagus
„ Taken in context of other findings

22. 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

23. Reflexes
„ Brainstem
„ Deep tendon
ƒ Biceps, brachioradialis, triceps
ƒ Patellar, Achilles
ƒ Plantar Responses
„ Superficial skin
ƒ Abdominal, cresmasteric

24. 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

25. 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

26. Coma Mimics
„ Akinetic mutism
„ ‘Locked-in’ syndrome
„ Catatonia
„ Conversion reactions

27. 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)

28. “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

29. 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

30. 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