Disorders of Consciousness
1.Somnolence: Excessive drowsiness; patient can be awakened.
2.Stupor: Patient responds only to strong stimuli.
3.Coma: Complete loss of consciousness with no purposeful response to stimuli.
- Causes: Brainstem lesions. Bilateral cerebral hemisphere lesions. Metabolic disorders
Consciousness - qualitative and quantitative disorders. Brain death.
Definition
Consciousness is the state of awareness of self and environment, dependent on:
- Ascending Reticular Activating System (ARAS) (brainstem → arousal)
- Cerebral hemispheres (awareness/content)
Normal consciousness = arousal + awareness
Components of Consciousness
1. Arousal (Wakefulness): Maintained by ARAS. Enables wake–sleep regulation
2. Awareness: Function of cerebral cortex. Includes perception, cognition, response
A. Quantitative Disorders of Consciousness
➡️ Reduction in level of consciousness
1. Somnolence (Lethargy): Excessive drowsiness. Patient awakens to verbal stimuli. Fully oriented but quickly falls asleep
2. Sopor (Obtundation): Marked reduction of consciousness. Arousal only with strong stimuli. Slow, incomplete responses
3. Stupor: Responds only to painful stimuli. No spontaneous speech. Protective reflexes preserved
4. Coma: Complete loss of consciousness. No response to verbal or painful stimuli. Eyes closed, no purposeful activity
- Causes: Stroke. Traumatic brain injury. Brainstem lesions. Metabolic/toxic disorders. Drug overdose
B. Qualitative Disorders of Consciousness
➡️ Content of consciousness is disturbed, level may be partially preserved
1. Delirium: Acute confusional state. Fluctuating attention. Disorientation. Hallucinations. Agitation
- Causes: Infection. Metabolic disturbances. Drug intoxication/withdrawal
2. Oneiroid State: Dream-like hallucinations. Distorted reality perception
3. Twilight State: Narrowed consciousness. Automatic behavior. Post-episode amnesia. Often epileptic origin
4. Confusion: Impaired thinking. Reduced attention and concentration. Disorientation
C. Special States of Consciousness
1. Vegetative State: Sleep–wake cycles preserved. Eyes may open. No awareness of self/environment. Brainstem functions intact
2. Minimally Conscious State: Minimal but definite awareness.Inconsistent responses
3. Locked-in Syndrome
- Lesion: ventral pons
- Conscious and fully aware. Quadriplegia + anarthria. Only vertical eye movements preserved
- Important: Consciousness is intact
D. Brain Death
Definition: Brain death is the irreversible cessation of all brain functions, including the brainstem.
Medically and legally = death
Diagnostic Criteria
1. Known Irreversible Cause: Massive brain injury. Intracranial hemorrhage. Severe hypoxic brain damage
2. Deep Coma: No response to external stimuli
3. Absence of Brainstem Reflexes: Pupillary light reflex absent. Corneal reflex absent. Oculocephalic reflex (doll’s eyes) absent. Oculovestibular (caloric) reflex absent. Gag reflex absent. Cough reflex absent
4. Apnea Test: No spontaneous breathing despite elevated CO₂. Confirms loss of respiratory drive