coma

Introduction

Depressed consciousness to the extent that the patient is unresponsive to noxious stimuli. (also see arousal)

Etiology

• diffuse insults to cerebral hemispheres*
• damage to reticular-activating system
• combination of cerebral hemisphere & brainstem dysfunction
• structural lesions, toxic, metabolic & infectious causes
• also see differential diagnosis of coma

* unlateral hemispheric lesions alone do not cause coma

Pathology

• persistent vegetative state follows a period of coma
• unaware of self or environment
• no purposeful response to stimuli, noxious or otherwise
• continuation of sleep-wake cycles & brainstem function

Physical examination

• Glasgow coma scale
• pupillary size
• ocular motility
  • doll's eyes
  • cold calorics
  • horizontal disconjugate gaze
    • cranial neuropathy
    • ipsilateral cerebral hemispheric lesion
    • ipsilateral pontine lesion
    • contralateral thalamic lesion
  • vertical disconjugate gaze
    • brain stem lesion
  • nystagmus suggests epileptiform activity

Clinical manifestations

• unaware of self & environment
• no response to noxious stimuli
• sleep-wake cycles & brainstem function may remain
• also see persistent vegetative state

Laboratory

• serum chemistries
  • electrolytes
  • serum glucose
  • serum Ca+2
  • urea nitrogen
  • plasma ammonia (NH3)
  • osmolality
• urine toxicology
• lumbar puncture & CSF examination
  • suspected meningitis or subarachnoid hemorrhage (normal neuroimaging)

Diagnostic procedures

• electroencephalogram (EEG) to exclude non-convulsive status epilepticus

Radiology

• urgent computed tomography (CT) to rule out hemorrhage, mass lesion
• magnetic resonance imaging (MRI)

Differential diagnosis

• locked-in syndrome
  • quadriplegic, mute, preserved vertical eye movements
• nonconvulsive status epilepticus, toxic, metabolic & infectious disorders
  • no focal neurologic signs, meningism or fever
• meningitis, meningoencephalitis, subarachnoid hemorrhage
  • meningismus, no focal neurologic signs
• stroke, hemorrhage, tumor, abscess
  • focal neurologic sign(s)
• brain death: coma, absence of brainstem reflexes, apnea

Management

• establish stable vital signs
  • airway, breathing, circulation
• administer urgent therapy for potentially reversible causes
  • glucose plus thiamine 100 mg IV
    • fingerstick for blood glucose can obviate the need
  • naloxone if opioid overdose is suspected
  • consider flumazenil
    • avoid in patients with seizure disorder
• endotracheal intubation for airway protection
• stabilize neck if evidence of trauma
  • evaluate cervical spine
• prognosis
  • patients with drug-induced or metabolic coma have the best prognosis: complete recovery is not uncommon
  • diffuse anoxic encephalopathy & focal structural disease have poorer prognosis
  • the most sensitive early (48 hours) markers of poor outcome after cardiac arrest (no sedation) are:
    • no pupillary response or corneal response
    • absence of motor response to pain
    • burst suppression pattern on electroencephalogram
  • death or severe disability in > 95% of patients with with abonormal brainstem responses or absent motor responses by day 3
  • patients with non-traumatic coma who do not improve within 1 month are unlikely to regain consciousness; beyond 3 months, recovery is extremely rare
  • overall, 15% of patients with non-traumatic coma have a satisfactory recovery
  • patients with traumatic coma are more likely to survive than patients with non-traumatic coma
  • after 10-14 days, patients may transition into vegetative state
  • patients with traumatic coma are more likely to regain consciousness despite prolonged coma lasting several months
  • also see outcomes of comatose patients after CPR
• consider organ donation in those patients who meet criteria for brain death

More general terms

• disorder of arousal; lack of awareness; impaired consciousness
• loss of consciousness (LOC)

More specific terms

• diabetic coma
• hepatic coma
• hyperglycemic-hyperosmolar syndrome; hyperglycemic-hyperosmolar nonketotic coma (HHNC)

Additional terms

• differential diagnosis of coma
• Doll's eye phenomenon (oculovestibular reflex)
• Glasgow coma scale (GCS)
• outcomes of comatose patients after cardiopulmonary resuscitation (CPR)
• persistent vegetative state

Patient information

coma patient information