Links: Key causes, Levels and ICD9 | W/u | CT Findings | Reflex Eye Movement (Dolls Eyes, Caloric Testing) | Pupils & Exam Clues | Posturing | Management | Ddx of Etiology | Pseudocoma & Catatonia & Minimally Conscious State | Persistent Vegetative State | Encephalopathy | See Delirium |
A state of profound unconsciousness from which on cannot be aroused (unarousable unresponsiveness). The pt does not open their eyes to stimulation or spontaneously, nor can they sustain visual pursuit movements when eyes are manually held open. They do not follow commands or demonstrate intentional movements.
PP: There are 3 basic mechanisms for all coma (and related states): supratentorial, infratentorial, diffuse metabolic, multifactorial. The “big three” causes are toxic/metabolic causes, trauma, and stroke.
1. Toxic/metabolic: causes diffuse cortical dysfunction. Metabolic encephalopathy is a general term used to describe any process that affects global cortical function by altering the biochemical function of the brain. Suspect when there is an altered cognitive status in the absence of focal neurologic signs or an obvious anatomic lesion such as an acute cerebrovascular accident or head injury. Commonly seen with hypoglycemia (ethanol, salicylates, beta-andrenergics), hypoxia, depressed neuronal function (GABA, opiate), toxins-induced sz with postictal state, structural lesion from a hematoma (cocaine, amphetamines). Intaventricular hemorrhage with or w/o hydrocephalus. Organ disease (lung, liver, kidney).
Acute metabolic derangement (Na <110 or >160 mmol/L, Ca >3.4 mmol/L, Mg >5 mcg/L, CO2 >70 mmHg, glucose <40 or >800 mg/dL).
2. Supratentorial: injury to the hemispheres. An expanding mass in the hemispheres eventually causes herniation lateral (uncal) herniation (as in subdural hematoma). It often compresses the oculomotor nerve causing an ipsilateral dilated pupil and ocular muscle paralysis (except for upward and lateral gaze – CN 4,6). Central herniation results in early unconsciousness with little effect on the pupils initially, then its path merges with late uncal herniation compressing the brainstem RAS (herniation) or hemorrhagic contusion from a fall.
3. Infratentorial: a mass lesion or stroke directly affecting the brainstem RAS – remember: RAS begins mid-pons and extends cephalad.
Damage to pons, medulla, cerebellum caused by basilar artery occlusion with pontine infarction, cerebellar infarction, posterior fossa subdural hematomas, pontine or cerebellar hemorrhages, various neoplasms, vertebrobasilar artery aneurysm, multiple myeloma, central pontine myelinolysis can result in upward tentorial herniation or downward herniation through the foramen magnum exam reveals bilateral weakness / paralysis, pinpoint pupils, dysconjugate gaze, irregular breathing or apnea.
Mental Function: aspects of nervous system function are responsible for the manner in which individuals interact with their environment. Mental function can be considered normal when all the following mental processes are intact:
1. Awareness of self and surroundings.
2. Accurate perception of what is experienced (orientation).
3. Ability to process input data to generate more meaningful information (judgment and reasoning).
4. Ability to store and retrieve information (memory).
Levels of Consciousness: two components: arousal (or wakefulness) and awareness (or responsiveness).
Spectrum of abnormal levels of consciousness:
Hyperalert –> Awake, anxious and agitated, or restless. R/o Manic, amphetamines etc.
* Consciousness (Normal Awake) – awake and aware of self and the environment. Generally cooperative, oriented, and tranquil.
* Somnolent –> easily aroused and aware. Sleep is a natural state of bodily rest from which the patient is rousable.
* Lethargy – decrease in responsiveness in a rousable patient. Awake but responds to commands only.
* Clouding of consciousness – very mild form of altered mental status in which reduced wakefulness may occasionally cause confusion.
* Confusion – a more serious alteration of the mental status in which patient may be disoriented, and may find it difficult to follow commands.
* Delirium – acute decline in attention, perception and cognition. It can be of a hyperactive or hypoactive variety.
* Obtunded –> Appears asleep (this is not true sleep) but responds briskly to a light glabellar tap or a loud auditory stimulus.
* Stuporous – an abnormal sleepy state from which the patient can be aroused by vigorous or repeated stimuli and when left undisturbed, the patient will immediately lapse back to the unresponsive state. Aroused with difficulty, impaired awareness. Pt is inattentive, drowsy, and unresponsive but can be aroused by vigorous stimuli for short periods. Responds only sluggishly to a light glabellar tap or a loud auditory stimulus.
* Coma – a state of unrousable unresponsiveness
Comatose –> unarousable and unaware and unresponsive. Appears asleep, with no response to stimuli. In pt’s with downward transtentorial herniation, the level of dysfunction is further characterized:
Diencephalic level: Reactive pupils . Early: Preserved oculocephalic responses. Late: Purposive response to pain.
Midbrain level: Decorticate response to pain. Fixed and midsized pupils. Abnormal oculocephalic responses. Decerebrate response to pain.
Lower brain stem level: Fixed and midsized pupils. Abnormal oculocephalic responses. No response of upper limbs to pain.
Vegetative state –> aroused but unaware. Produced by diffuse cerebral injury without involvement of the brainstem reticular activating system (which determines arousal). In this condition, the pt is awake (eyes open) but is unresponsive to verbal or noxious stimuli. A condition that can mimic the vegetative state is called the locked-in syndrome. This ‘wakefulness’ is accompanied by reflexive motor activity only, devoid of any voluntary interaction with the environment, the condition is called a vegetative state. The vegetative state may be a transition to further recovery, or not (for a succinct review of ethical and legal problems in Persistent Vegetative State. Signs of voluntary motor activity should be actively searched for in vegetative state pt’s, as they herald the minimally conscious state (MCS). Brain response to one’s own name (preserved semanctic processing) can be observed in noncommunicationg brain-damaged pt’s (Arch Neurol 2006;63:562-9) (auditory evoked potentials, P3 component) (including pt’s with MCS, Locked-in syndrome and PVS).
ICD-9 Codes:
780.01 Coma
780.02 Transient alteration of awareness
780.03 Persistent vegetative state
780.09 Drowsiness – Stupor
• With a decreasing level of consciousness, a person’s ability to distinguish between self and nonself referential stimuli also decreased, with concomitant changes in activity in certain areas of the brain (22nd Meeting of the European Neurological Society (ENS). Abstract O-236. Presented June 10, 2012)…..compared to other names, the own name elicits a greater activation that you don’t see with other names in the medial prefrontal cortex area as well as the posterior cingulate cortex…and the thalamus, which are as well implicated in this…internal awareness.”….In states of mild sedation, there was still “a little bit of activation” in this self-related brain area, and during unconsciousness, all the activation disappeared. But there was still residual activity in the primary auditory cortices and superior temporal gyri with all the stimuli.
Key tests: HCT, WBC, lytes (Na, K, Cl, CO2, Ca, P), glucose, BUN & Cr, AST, GGT, osmolality.
Optional: ammonia, anticonvulsant/ Li/ Salicylate/ Acetaminophen levels, ABG (pH, PO2, PCO2, HCO3, Hb CO), TSH, Tox screen of Urine/ Blood, LP, blood/ CSF Cx, PT/ PTT, platelets.
Exam Components: pupils, eye mov’t, motor response, respirations.
1. Pupils and other physical clues |
2. Reflex Eye Movements (Dolls Eye, Calorics) |
3. Posturing |
4. Vital signs: Clinical findings might help physicians to distinguish between pt’s with and w/o anatomic brain lesions: mean SBP & DBP levels were significantly higher and mean pulse rate was significantly lower in pt’s with brain lesions than in those w/o lesions (Using vital signs to diagnose impaired consciousness: Cross sectional observational study. BMJ 2002;325:800-2).
5. Respiratory pattern: Cheyne-Stokes from bilateral or diencephalic insult anywhere from forebrain & pons. If stable have good prognosis, but if unilateral mass lesion, may signify impending herniation. Central neurogenic hyperventilation: usually due to lesion of the central tegmentum of the pons, ventral to the aqueduct/ 4th ventricle. RR of 40-70/min. Apneustic breathing: a prolonged inspiratory gasp with a pause at the end of inspiration. Due to lesion of the dorsolateral lower half of the pons. Cluster breathing is periodic with irregular frequency and amplitude with variable pauses. Due to high medullary lesion. Ataxic breathing is irregular in rate and rhythm and due to a medullary lesion, often preterminal.
ABCDEE Exam for the Comatose Patient:
Detects any of the five H’s that threaten the brain: Hypoxia, Hypotension, Hypoglycemia, Hyperthermia, and Herniation.
1. A and B = Airway and Breathing. Ensure that the Pt has an open airway and is breathing. Otherwise the brain, which requires a continuous supply of O2 and glucose, will start to die within 5 minutes of total oxygen deprivation.
2. C = Circulation. The blood must circulate to deliver O2 and glucose to the brain.
Breathing and circulation must be restored within minutes.
3. D = Dextrose. The circulating blood must contain enough dextrose to nourish the brain.
4. EE = Examine the Eyes. Examination of pupillary size and reactions, the optic fundi, and the position and movement of the eyes spontaneously and in response to the vestibulo-ocular reflex reveals more about the neurologic status of the unconscious Pt than any other steps in the examination. Fixed pupils and fixed eyes indicate trouble.
5. Measure the body temperature.
Other: CN’s V & VII can be assessed in comatose pt’s by testing corneal reflexes and by observing facial grimacing in response to noxious stimulation (supraorbital pressure or nasal tickle). CN’s IX & X can be assessed by testing the gag reflex (absent in 20% of normal subjects).
• A study with 407 pt’s found that all with bilaterally absent early cortical response (N20 = an electrophysiologic variable median nerve somatosensory evoked potential = SSEP) responses or serum neuron specific enolase (NSE) >33 µg/L at any point during the study did poorly, but not all pt’s who had poor outcomes were identified by either of these two findings (Neurology 2006;66:62-8). The American Academy of Neurology has given a level-B recommendation for prognostication with these tests (Neurology 2006; 67:203)….these tests offer a prognostic crystal ball that may conserve resources and save families from the torment of protracted false hope, which can be worse than the shock of no hope at all.
Sepsis, DIC, pancreatitis, vasculitis, TTP, fat emboli, diffuse micrometastases, sz (prolonged post-ictal), basilar/ brainstem/ cerebellar stroke, malingering, conversion d/o, subarachnoid hemorrhage, bacterial meningitis, encephalitis, subdural empyema, hypo/hyperthermia.
Exogenous toxin –> toxin ETOH, psychotropic drug, opioid, salicylate, anticholinergic, Penicillins, clonidine OD, CO, cyanide, Met-Hb.
Endogenous toxin –> incr Ca, hypoxia, hypoglycemia, hepatic/uremic encephalopathy, pulmonary insufficiency (incr CO2), osmolar agent (hyper glycemia, hyper/hyponatremia).
Abnormal CT Findings:
Mass lesion (shift, herniation) –> hematoma, hemorrhagic contusion, MCA infarct.
Hemorrhage in basal cisterns –> aneurysmal SAH, cocaine abuse.
Intraventricular hemorrhage –> AVM or CVA.
Multiple hemorrhagic infarcts –> cerebral venous thrombosis.
Multiple cerebral infarcts –> Endocarditis, coagulopathy, CNS vasculitis.
Diffuse cerebral edema –> cardiac arrest, fulminant meningitis, acute hepatic necrosis, Reye’s syndrome, encephalitis.
Acute hydrocephalus –> aqueduct obstruction, colloid cyst, pineal region tumor.
Pontine or cerebellum hemorrhage –> HTN, AVM, cavernous malformation.
Ddx Single Intracranial Mass:
Not immunocompromised –> astrocytoma, oligodendroglioma, glioblastoma multiforme, solitary met, bacterial abscess, sarcoid, giant aneurysm, histoplasmosis, coccidiomycosis, blastomycosis, MS, meningioma, radiation necrosis.
If immunocompromised –> Toxo, lymphoma, PML, aspergillus, mucormycosis, nocardia, cysticercosis, echinococcus, schistosomiasis, amebiasis, mycobacteria.
