Evaluation of Patients in Coma

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Evaluation of Patients in Coma

• Liam Durcan MD FRCPC
• Department of Neurology and Neurosurgery

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What Well Cover

• Basic definitions
• Key exam points
• Epidemiology of Coma
• Coma mimics

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What we wont talk about

• Brain death/ chronic vegetative state
• toxidromes
• really complex neuroanatomy
• Exhaustive lists of causes
• Basic Resuscitative Care

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Definitions

• Coma Unarousable unresponsiveness in which the
  subjects lie with eyes closed
• Plum and Posner- Diagnosis of Stupor and Coma
• Other terms obtundation, stupor
• fallen out of favour because of imprecision
• descriptive methods favoured

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Consciousness

• Two components of conscious behavior
• content- the sum of cognitive and affective
  function
• arousal- appearance of wakefulness
• Content depends on arousal but normal arousal
  does not guarantee normal content

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Really Simple Neuroanatomy

• Arousal where is it localized?
• Ascending Reticular Activating System (ARAS)
  core of the brainstem
• receives input from numerous somatic afferents
• projects to midline thalamic nuclei (which are in
  a circuit with cortical structures) and the
  limbic system

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ARAS

• ARAS acts as a gating system, increasing or
  decreasing thalamic inhibitory influence on the
  cortex
• alters effect of sensory stimuli ascending
• alters descending cortical stimulation

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Demands of Arousal

• Function of ARAS-Thalamic-Cortical system depends
  on
• anatomic integrity of structures
• metabolic integrity (circulatory integrity)
• communicative integrity (neurotransmitter
  function)

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Coma Fact Number One

• Coma implies dysfunction of
• ARAS or
• Both hemi-cortices
• Anatomically, this means
• central brainstem structures (bilaterally) from
  caudal medulla to rostral midbrain
• both hemispheres

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Epidemiology of Coma

• Plum and Posner 1982
• 500 consecutive cases of coma
• 101 supratentorial (44/101 ICH)
• 65 subtentorial lesions (40/65 brainstem
  infarcts)
• 326 diffuse or metabolic brain dysfunction
• 149 drug intoxication

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Clues from History

• Onset of symptoms
• sudden onset
• fluctuations
• Associated neurologic symptoms
• Medications

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Neurologic Exam

• Cornerstone of assessment
• Descriptive, systematic
• Reference point for serial assessment

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Exam goals

• Primary CNS event versus secondary
• Implications
• short and long-term outcome
• investigations

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Breathing

• Abnormalities of respiration can help localize
  but almost always in the context of other signs
• Central-reflex Hyperpnea (midbrain-hypothalamus)
• Apneustic, cluster, Ataxic (Lower pons)
• Loss of automatic breathing (medulla)

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Cranial Nerve Exam

• Systematic assessment of brainstem function via
  reflexes
• Cranial Nerve Exam
• Pupillary light response (CN 2-3)
• Occulocephalic/calorics (CN 3,4,6,8)
• Corneal reflex (CN 5,7)
• Gag refelx (CN 9,10)

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.Pupillary Light Responses

• Afferent Limb Optic Nerve
• Efferent Limb Parasympathetics via occulomotor
• Midbrain integrity/ tectum
• Uncal Herniation (3rd nerve dysfunction)
• Pupillary resistance to insult

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Pupillary Light Responses

• Be aware of drug effects
• Systemic and Local
• Avoid PERLA
• State size, before and after light stimulation
• Specify right and left

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Pupils Localizing Value

• Pons-pinpoint pupils
• Symp. Dysfinction plus parasymp.irritation
• Midbrain-Large fixed pupils unresponsive to
  light, hippus
• Horners- symp.dysfunction
• Unilateral dilation- parasymp. Dysfunction
  usually due to 3rd nerve lesion

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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

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Corneal Reflex

• Afferent Trigeminal Nerve
• Efferent Third Nerve (Bells Phenomenon
• and Facial Nerve (Eye closure)
• Tests dorsal midbrain (Bells) and pontine
  integrity (Eye closure)

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Eye Movements

• Before maneuvers attempted note resting position
• Midline
• Deviation suggests frontal/pontine damage
• Conjugate
• Dysconjugance suggests CN abn.
• Moving
• Roving, dipping, bobbing

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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

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Occulcephalic Reflex

• Brisk rotation of head with eyes held open
• Watch for contraversive movements
• Next
• Flexion eyes deviate up and eyelids open (dolls
  head phenomenon)
• Extensioneyes deviate downward

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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
• Awake deviation toward,nystagmus away
• Comatose deviation toward
• Wait 5 minutes, do other ear

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Calorics

• Watch for conjugance of deviation
• To test vertical eye movements
• Both ears, cold water-downward gaze
• Both ears, warm water-upward gaze

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Gag Reflex

• Afferent Glossopharyngeal
• Efferent Vagus
• Taken in context of other findings

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Motor Exam

• Assess tone, presence of asterixis
• Response to painful stimuli
• none
• abnormal flexor
• abnormal extensor
• normal localization/withdrawal
• Avoid use of decerebrate/ decorticate

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Reflexes

• Brainstem
• Deep tendon
• Biceps, brachioradialis, triceps
• Patellar, Achilles
• Plantar Responses
• Superficial skin
• Abdominal, cresmasteric

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Uncal herniaiton

• Expanding lesions in lateral middle fossa
• Compression of hippocampal gyrus over free edge
  of tentorium
• Three stages described
• Early third nerve
• Late third nerve
• Midbrain-Upper pons stage

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Goals in Emergency

• Primary Neurological Process?
• evidence of raised ICP
• focal findings, especially that implicate
  brainstem structures
• Secondary Processes
• signs of infection, toxic/metabolic processes
• relative lack of focality

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Coma Mimics

• Akinetic mutism
• Locked-in syndrome
• Catatonia
• Conversion reactions

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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)

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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

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Catatonia

• Symptom complex associated with severe
  psychiatric disease with
• stupor, excitement, mutism, posturing
• can also be seen in organic brain diease
  encephalitis, toxic and drug-induced psychosis

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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