Neurology · MU Sofia

22. Consciousness: qualitative and quantitative disorders, brain death

Covers disorders of consciousness, starting with the two components of normal consciousness (arousal from the ARAS and awareness from the cortex). It then sets out quantitative disorders such as somnolence, sopor, stupor and coma, followed by qualitative ones like delirium, oneiroid state, twilight state and confusion. Special states including the vegetative state, minimally conscious state and locked-in syndrome come next, ending with brain death and its diagnostic criteria: the cause, deep coma, brainstem reflexes and the apnoea test.

Inside: 2 sections · 16 flashcards · 3 min

Topic 22 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 2 sections, about 369 words (3 min of reading), with 16 flashcards.

In this note

  1. Disorders of Consciousness
  2. Consciousness - qualitative and quantitative disorders. Brain death.

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

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