Coma and Movement Disorders

What is consciousness, and what are its two components?

Consciousness is awareness of self and environment, requiring both arousal and mental content, and depends on the integrity of the reticular activating system and cerebral cortex.

Content is the sum of cognitive and affective mental function (a function of both cerebral cortices), while arousal is the appearance of wakefulness (a function of the ascending reticular activating system).

Content depends on arousal, but normal arousal does not guarantee normal content — arousal damage leads to coma, semi-coma, or delirium, while content damage leads to dementia, delusions, confusion, or inattention.

What is the spectrum of consciousness, from alert to coma?

Alert/conscious: perfectly normal arousal.
Sleep: the only normal form of altered consciousness.
Lethargy: lies between alertness and stupor, with difficulty maintaining alertness.
Stupor: baseline unresponsiveness requiring repeated vigorous stimuli (verbal or motor) to achieve arousal.
Delirium: acute disturbance of attention with disturbed cognition (memory deficit, disorientation, language, visuospatial, or perceptual impairment) and clouded consciousness.
Semi-coma: response to motor stimulus only (not verbal).
Coma: complete unresponsiveness to arousal.

What is the neuroanatomy and pathogenesis of coma?

The Ascending Reticular Activating System (ARAS), the core of the brainstem, receives input from somatic afferents (acting as a gate) and projects to the thalamus and limbic system, and from there to both cerebral cortices.

Coma implies dysfunction of either the ARAS or both cerebral hemi-cortices, anatomically corresponding to bilateral central brainstem structures (from caudal medulla to rostral midbrain) or both hemispheres.

What are the differentiating features and causes of toxic-metabolic coma?

Toxic-metabolic coma accounts for about 2/3 of coma cases.

Differentiating features:
confusion/stupor commonly precedes motor signs; motor signs and ocular reflex findings are usually symmetrical;
pupillary light reflex is usually preserved;
asterixis, myoclonus, tremor, and seizures are common; acid-base imbalance with hyper/hypoventilation is frequent.

Causes: deprivation of oxygen/substrate/cofactor (hypoxia, diffuse ischemia, hypoglycemia, thiamine deficiency/Wernicke-Korsakoff);
disease of other organs (hepatic coma, uremia, CO2 narcosis, pancreatic disease, thyroid disease, adrenal disease, sepsis);
exogenous poisons (sedatives, narcotics, psychotropics, methyl alcohol, ethylene glycol, anticonvulsants, heavy metals, cyanide); and
electrolyte abnormalities (sodium, acid-base, magnesium, calcium, phosphorus).

What are the differentiating features of structural coma (supratentorial vs infratentorial), and what is the psychiatric cause of coma-like states?

Structural coma accounts for about 1/3 of cases.
Supratentorial lesions cause coma via widespread bilateral disease, raised ICP, or herniation, with initiating signs of focal cerebral dysfunction and often asymmetrical motor signs; causes include hematoma, neoplasm, abscess, contusion, vascular accidents, and diffuse axonal injury.

Infratentorial lesions involve the RAS directly, with a history of preceding brainstem dysfunction, localizing brainstem signs (always including oculovestibular abnormality), cranial nerve palsies, and bizarre respiratory patterns at onset; causes include neoplasm, vascular accidents, trauma, cerebellar hemorrhage, and central pontine myelinolysis.

A unilateral dilated pupil unresponsive to light indicates uncal herniation until proven otherwise.

The psychiatric cause is catatonia (mute, with marked decrease in motor activity).

What conditions must be differentiated from coma, and what are the criteria for diagnosing brain death?

Coma's differential diagnosis includes: brain death, persistent vegetative state, locked-in syndrome, thalamic lesions, nonconvulsive status epilepticus, and psychiatric unresponsiveness.

Brain death is the irreversible loss of brain and brainstem function, where the cause of coma is known and sufficient (e.g., cardiopulmonary arrest), with no improvement after observation (at least 6 hours in adults, 12 hours to 2 days in children).

It requires absence of ALL brainstem reflexes (corneal, pupillary light, gag, oculocephalic/Doll's sign, vestibulo-ocular/caloric) plus absent spontaneous respiration (abnormal apnea test: no breaths despite pCO2 >60 mmHg on 100% oxygen), and exclusion of reversible causes (hypothermia ≤32°C, hypotensive shock, drug intoxication especially barbiturates, severe metabolic disturbance).

Ancillary tests supporting diagnosis: flat-line EEG and absent cerebral blood flow (transcranial doppler or radioisotope scan).

What are the diagnostic criteria for persistent vegetative state?

No awareness of self or environment;
no interaction with others; no evidence of sustained, reproducible, purposeful, or voluntary behavioral responses to visual, auditory, tactile, or noxious stimuli;
no evidence of language comprehension or expression;
intermittent wakefulness with preserved sleep/wake cycles;
bowel and bladder incontinence;
preserved autonomic functions;
and variably preserved cranial nerve (pupillary, oculocephalic, corneal, vestibulo-ocular, gag) and spinal reflexes.

What characterizes locked-in syndrome, nonconvulsive status epilepticus, and psychiatric unresponsiveness?

Locked-in syndrome:
the patient may appear vegetative but is "de-efferented" — unable to move limbs, face, or gaze laterally — while vertical gaze and eyelid blinking are preserved, allowing communication (one blink for yes, two for no); it is caused by extensive pontine infarction.

Nonconvulsive status epilepticus presents with continued/persistent generalized seizure activity without obvious convulsions, with subtle signs like rhythmic nystagmus or eyelid/facial/limb twitching, diagnosed by emergent EEG and response to IV benzodiazepine.

Psychiatric unresponsiveness is rare and a diagnosis of exclusion, requiring: no drug overdose history, intact brainstem reflexes, spontaneous breathing, no focal neurological deficit, normal metabolic profile, normal brain MRI (DWI), and normal (awake-pattern) EEG.

What key general examination findings help evaluate a comatose patient, and how is level of consciousness best assessed?

Temperature: fever suggests infection or heat stroke;
hypothermia suggests cold exposure (especially with alcoholism), hypothyroidism, hypoglycemia, sepsis, or rarely a primary brain lesion.

Pulses: asymmetry suggests dissecting aneurysm.

Head: inspect/palpate scalp for trauma;
blood in the ear canal (Battle sign) or around the eyes (raccoon sign) suggests skull fracture; inspect ears/nose for blood or CSF.

Rather than vague terms like "stupor" or "obtunded," it is more useful to describe the patient's spontaneous behavior and response to stimuli — the Glasgow Coma Scale (GCS) provides a structured hierarchy of eye, verbal, and motor responses reflecting coma severity.

What do different pupillary findings indicate in a comatose patient?

Parasympathetic lesions (e.g., oculomotor nerve compression in uncal herniation or aneurysm) cause pupil enlargement, ultimately full dilation with no light reaction.

Sympathetic lesions cause Horner syndrome (miosis, ptosis, anhidrosis).

Pinpoint but reactive pupils suggest pontine hemorrhage or opiate intoxication.

Fixed, dilated pupils (confirmed with bright light) may indicate anticholinergic drugs (atropine, glutethimide, amitriptyline, antiparkinsonian agents), hypothermia, severe barbiturate intoxication (these last two can mimic brain death reversibly), ongoing/recent seizure (may be unilateral), or an anoxic-ischemic event (implies poor prognosis).

Fundus papilledema indicates raised intracranial pressure.

What do eye movement and blinking findings reveal in a comatose patient?

Preserved oculocephalic and oculovestibular (caloric) reflexes in a comatose patient indicate preserved brainstem function.

Dysconjugate eyes at rest suggest individual muscle paresis, internuclear ophthalmoplegia, or a preexisting tropia/phoria.

Conjugate lateral eye deviation toward one side indicates a lesion in the contralateral brainstem or the ipsilateral cerebral hemisphere.

Persistent rhythmical nystagmus is a subtle sign of nonconvulsive status epilepticus.

Spontaneous blinking indicates an intact ARAS, while in locked-in syndrome only blinking and vertical eye movements remain.

What respiratory patterns are seen in coma, and what do they localize?

Cheyne-Stokes respiration (alternating crescendo-decrescendo hyperventilation and apnea): bilateral cerebral disease, including impending transtentorial herniation, upper brainstem lesions, or metabolic encephalopathy.

Sustained hyperventilation: usually metabolic acidosis, pulmonary congestion, or hepatic encephalopathy.

Apneustic breathing (inspiratory pauses): pontine lesions (especially infarct), rarely metabolic coma or herniation.

Ataxic (Biot) breathing (irregular rate/amplitude): medullary damage.

Stertorous breathing (inspiratory noise): airway obstruction.

Odor clues: acetone, alcohol, or fetor hepaticus can also aid diagnosis.

What do motor examination findings, posturing, and neck signs reveal in coma?

Asymmetrical limb movements or tone suggest a structural brain lesion.

Decorticate posturing points to supratentorial lesions, while decerebrate posturing points to infratentorial lesions.

Bilateral myoclonic jerks suggest toxic-metabolic causes of coma.

Stiff neck on passive flexion (not rotation/tilting) suggests meningitis, subarachnoid hemorrhage, or foramen magnum herniation, while resistance in all directions suggests bone/joint disease (cervical fracture must be excluded first).

What are the two traditional patterns of brain herniation, and what do they signify?

Transtentorial herniation occurs with expanding supratentorial mass lesions and follows

two patterns:
the uncal pattern, which starts with a unilateral dilated, unreactive pupil, and
the central pattern, which starts with impairment of consciousness.

What investigations are used in the workup of a comatose patient?

CT or MRI should be performed promptly if coma is unexplained, and before lumbar puncture if the exam suggests a focal lesion.

Lumbar puncture should be performed promptly if coma is not explained by imaging (cautiously if imaging is unavailable and no mass lesion is suspected).

Emergency labs: glucose, sodium, calcium, BUN, creatinine, arterial pH/PCO2/PO2, other electrolytes, liver function tests, blood/CSF cultures, blood or urine toxicology screening, and coagulation studies as indicated.

EEG can distinguish true coma from psychic unresponsiveness or locked-in state (always abnormal in true coma) and may reveal asymmetry or unsuspected seizure activity.

What are the "golden rules" and initial steps in managing a comatose patient?

Golden rules:
all alterations in arousal are acute life-threatening emergencies requiring urgent determination of the cause and its evolution, and protection of the brain from further damage; coma should NEVER be managed at home;
ABCs (Airway, Breathing, Circulation) are the first priority, identifying and addressing life-threatening inadequacies before addressing CNS causes; rapidly progressive metabolic disorders like hypoglycemia must be treated urgently; and signs of intracranial hypertension/impending herniation must be evaluated and treated.

Initial steps: maintain ABC; urgently correct hypothermia; stabilize the cervical spine if trauma is suspected; give IV thiamine (at least 100 mg); rule out hypoglycemia with fingerstick glucose or empirical 50% dextrose; and check basic bloodwork/urine toxicology (CBC, electrolytes, glucose, renal/liver function, PT/PTT/INR, ABG, CO level if suspected).

How are movement disorders defined and classified?

Movement disorders are neurologic syndromes with either an excess of movement or a paucity of voluntary/automatic movements, unrelated to weakness or spasticity.

They are classified into:
hypokinetic disorders (paucity of movement) — parkinsonism; and
hyperkinetic disorders (abnormal involuntary movements) — dystonia, tremor, chorea, hemiballismus, tics, myoclonus, and tardive dyskinesia.

What is parkinsonism, and what are its idiopathic, symptomatic, and "Parkinson-plus" causes?

Parkinsonism is a clinical entity characterized by a quadriad of bradykinesia (slowness of motor function), tremor, rigidity, and postural instability.

Causes:
1) Idiopathic (Parkinson disease);
2) Symptomatic — atherosclerosis, drugs (antipsychotics, reserpine), toxins (carbon monoxide, manganese), trauma (repeated head injury), post-encephalitic (encephalitis lethargica), and metabolic (Wilson's disease — copper metabolism disorder with early onset, mental changes, Kayser-Fleischer corneal ring, dystonia, and static/kinetic tremors);
3) Parkinson-plus syndromes (atypical parkinsonism) — cortical basal ganglionic degeneration, dementia syndromes (Alzheimer's, diffuse Lewy body disease, frontotemporal dementia), multiple system atrophy syndromes (striatonigral degeneration, Shy-Drager syndrome, olivopontocerebellar degeneration), and progressive supranuclear palsy.

What is the epidemiology, pathology, and pathophysiology of Parkinson's disease?

Prevalence is approximately 120 cases per 100,000 population, with an average onset age around 60 years (onset before 40 is uncommon), and it is about 1.5 times more common in men.

The main pathology is loss of pigmented dopaminergic cells in the substantia nigra and other brainstem centers, along with eosinophilic intraneural Lewy body inclusions in the basal ganglia and brainstem (not seen in post-encephalitic parkinsonism).

Pathophysiology: normally dopamine and acetylcholine are balanced in the basal ganglia; in PD, dopamine decreases while acetylcholine remains normal, causing imbalance. The exact cause of idiopathic PD is unknown, likely a combination of genetic and environmental factors varying between individuals.

What is the classic tremor of Parkinson's disease, and how does it evolve and present?

PD is a gradual, progressive disorder that usually starts asymmetrically, with tremor as one of the four cardinal features.

The tremor begins in one upper limb, later involves the corresponding lower limb, and after a further interval spreads to the opposite side.

It affects distal segments most: in the upper limbs, rhythmic flexion/extension of the fingers or forearm pronation-supination, starting at the metacarpophalangeal joint, sometimes combined with thumb movement ("pill-rolling") and wrist involvement; in the lower limbs, most marked at the ankle; and in the jaw, opening/closing of the mouth.

Features: coarse, 4–7 Hz frequency; occurs at rest; increases with emotion/stress; decreases with voluntary action; and disappears during sleep.

What characterize bradykinesia, rigidity, and postural instability in Parkinson's disease, and what other motor features occur?

Bradykinesia: slow movement and reaction time, slowing of daily activities — in the arms, starting distally with decreased finger dexterity (difficulty buttoning, typing); in the legs, leg dragging, shuffling steps, unsteadiness, and difficulty rising from a chair or car.

Rigidity: increased resistance to passive movement present throughout the range of motion, best detected at the wrist or forearm;
cog-wheel rigidity occurs when tremor is present (interrupted character),
while lead-pipe rigidity occurs when tremor is absent (smooth resistance).

Postural instability: typical in late stages, causing impaired balance, frequent falls, and secondary fractures.

Other features: masked facial expression, hypophonia (slow monotonous speech), dysphagia, sialorrhea, micrographia, severe anterior thoracolumbar spine flexion, and difficulty turning in bed.

What non-motor features occur in Parkinson's disease?

Autonomic symptoms: skin flushing, excessive facial greasiness, and increased salivation.

Neuropsychiatric manifestations: dementia (prevalence increases with disease duration, reducing quality of life), mood changes (depression, apathy, anxiety), psychotic symptoms (hallucinations or delusions in about 4% of PD patients), and sleep disturbances.

What are the drug and surgical treatment options for Parkinson's disease?

Replacement therapy:
levodopa/carbidopa (Sinemet), the mainstay of treatment, replacing dopamine.
Dopamine agonists (e.g., bromocriptine) act directly on dopamine receptors but are less effective than levodopa, used early or as adjuvant therapy.
Anticholinergic drugs (trihexyphenidyl HCl, benztropine) provide good tremor relief but do not meaningfully improve bradykinesia or rigidity.
MAO-B inhibitors (selegiline) block dopamine breakdown, prolonging its action. COMT inhibitors (e.g., entacapone) prevent levodopa breakdown, prolonging the levodopa dose's duration of action.
Amantadine, an antiviral drug, is also used.
Surgery for severe refractory cases includes deep brain stimulation and palliative thalamotomy or pallidotomy, along with physiotherapy.

What is tremor, how are rest and action tremors classified with their causes, and what characterizes essential tremor?

Tremor is a rhythmic, regular movement at a joint from alternating contraction of a muscle group and its antagonist — the most common involuntary movement.

Rest tremor causes:
Parkinson disease, other parkinsonian syndromes, and secondary parkinsonism (toxic-CO, drug-induced, vascular/multi-infarct, traumatic/pugilistic encephalopathy, tumor/paraneoplastic, infectious/post-encephalitic/AIDS, metabolic/hypoparathyroidism).

Action tremor causes: postural tremors (physiologic, enhanced physiologic tremor from anxiety/fear/exercise/sleep deprivation/thyrotoxicosis, or essential tremor) and

kinetic tremors (cerebellar disorders like MS, trauma, stroke, drugs/toxins, or midbrain lesions).

Essential tremor typically affects people over 40, begins gradually in the hands/arms (sometimes head/voice), is postural and kinetic (resolving at rest), improves temporarily with alcohol in 50-70% of cases, worsens with stress/fatigue/caffeine/temperature extremes, and shows no bradykinesia or rigidity; it is familial in 50-70% of cases (autosomal dominant), with no pathologic findings, and is treated with propranolol or topiramate.

What are the causes and clinical features of chorea, and what is Huntington's disease?

Chorea consists of sudden, jerky, quite irregular movements in form, site, and timing, involving the extremities, face, trunk, and sometimes tongue; it occurs at rest, worsens with emotional stress and voluntary activity, and disappears in sleep,
with decreased tone (hypotonia),
a boat/scaphoid-shaped hand (wrist flexion with MCP/IP overextension and finger fanning on arm extension), and
a pronator sign (arm deviates downward/laterally and pronates when elevated/supinated).

Causes:
hereditary (Huntington's disease) and acquired (Sydenham's/rheumatic chorea, drug-induced [levodopa, lithium], metabolic [Wilson's disease], post-kernicterus, post-anoxia/hemorrhage in neonates, and vasculitis [SLE]).
Huntington's disease is an autosomal dominant hereditary disorder (incidence 5/100,000), gradual and progressive, starting insidiously with choreic movements and hypotonia followed years later by mental changes;

diagnostic signs are early middle-age onset, positive family history, progressive chorea, and progressive dementia; diagnosis is via genetic testing and MRI (showing cortical and caudate atrophy);

treatment uses dopaminergic antagonists (haloperidol) or dopamine-depleting agents (tetrabenazine).

What are hemiballismus, dystonia, athetosis, myoclonus, tics, and tardive dyskinesia?

Hemiballismus: a violent hemichorea affecting more proximal joints with wide excursions, starting suddenly in middle/old age from a vascular lesion usually of the subthalamic nucleus.

Dystonia: sustained or repetitive muscle contractions causing twisting movements or abnormal fixed postures, usually increased with action.

Athetosis: slow, twisting "mobile spasm" movements, more prominent distally in the limbs, affecting one or both body sides, with increased tone and variable rigidity.

Myoclonus: brief, shock-like jerking muscle contractions, single or repetitive, focal or generalized, often stimulus-sensitive (triggered by noise, movement, or light).

Tics: quick, coordinated, repetitive movements involving the same muscle group (e.g., eye blinking, neck twisting, shoulder shrugging, throat clearing) — the only involuntary movement a patient can voluntarily suppress briefly.

Tardive dyskinesia: persistent abnormal involuntary movements from chronic antipsychotic drug exposure, typically involving the lower face as repetitive orolingual-buccal dyskinesia resembling continuous chewing.