ALTERED MENTAL STATUS (AMS)

1. DEFINITION

Altered Mental Status (AMS) is a broad clinical syndrome representing any deviation from normal cognition, consciousness, attention, or behavior.

Includes:

• ↓ Level of consciousness (LOC)
• Cognitive dysfunction (confusion, disorientation)
• Behavioral abnormalities (agitation, psychosis)

 2. LEVELS OF CONSCIOUSNESS 

 3. CORE PATHOPHYSIOLOGY

AMS occurs due to dysfunction of:

 1. Ascending Reticular Activating System (ARAS)

• Located in brainstem
• Maintains wakefulness

 2. Bilateral Cerebral Hemispheres

• Responsible for awareness, cognition

4. ETIOLOGICAL CLASSIFICATION 

A. STRUCTURAL CAUSES

 Causes:

• Intracranial hemorrhage (ICH, SAH, SDH, EDH)
• Ischemic stroke
• Brain tumor
• Brain abscess
• Traumatic brain injury
• Hydrocephalus
• Herniation syndromes

 Clues:

• Focal neurological deficit
• Unequal pupils
• Abnormal posturing
• Sudden onset

 B. NON-STRUCTURAL (METABOLIC / TOXIC) CAUSES

Causes (Mnemonic: AEIOU-TIPS)

ICU Causes:

• Hypoglycemia / hyperglycemia
• Hyponatremia / hypernatremia
• Hepatic encephalopathy
• Uremic encephalopathy
• Sepsis-associated encephalopathy
• Drug toxicity (sedatives, opioids)

 FOCAL vs DIFFUSE

HISTORY TAKING 

1. Baseline mental status
2. Time course (onset, progression)
3. Precipitating events
4. Associated symptoms (neurological, infectious, metabolic)
5. Drug/toxin exposure
6. Past medical history
7. Travel and exposure history
8. Collateral history from attendants”

 1. FIRST PRINCIPLE: ESTABLISH BASELINE

• Baseline mental status:
• Normal / dementia / psychiatric illness?
• Functional baseline:
• Independent vs dependent
• Cognitive baseline:
• Known Alzheimer’s disease
• Prior strokes / epilepsy

Why important:

• Distinguishes acute AMS vs chronic impairment
• Helps diagnose Delirium (acute change from baseline)

 2. TIME COURSE OF AMS 

• Exact time of onset
• Sudden vs gradual
• Progression: improving / worsening / fluctuating
• Episodic vs continuous

3. PRECIPITATING EVENTS

• Trauma? (head injury)
• Fall / road accident
• Seizure before AMS?
• Fever preceding?
• Alcohol/Poison ingestion/Drug ingestion / overdose?

 4. ASSOCIATED SYMPTOMS (SYSTEM-WISE)

 Neurological

• Headache → raised ICP, meningitis
• Vomiting → ICP
• Focal deficit → stroke
• Seizures → epilepsy, metabolic
• Neck stiffness → meningitis

 Infectious

• Fever/Chills/Rash (meningococcemia)/Recent infection

 Cardiovascular

• Chest pain → MI → hypoperfusion
• Palpitations → arrhythmia
• Syncope history

 Respiratory

• Dyspnea → hypoxia,CO exposure (closed room heater)

 Metabolic

• Polyuria / polydipsia → Diabetic ketoacidosis
• Weight loss → malignancy
• Vomiting/diarrhea → electrolyte imbalance

 5. PAST MEDICAL HISTORY

• Diabetes → hypoglycemia / DKA
• Hypertension → stroke
• Liver disease → hepatic encephalopathy
• Kidney disease → uremia
• Epilepsy → seizures

 6. TOXICOLOGICAL HISTORY

• Suicide attempt/Occupational exposure/Gas exposure (CO)/Pesticides (important in India)

 7. TRAVEL & EXPOSURE HISTORY

• Malaria endemic area(Cerebral malaria
• )/TB exposure(Tuberculous meningitis)/Recent travel

 8. NUTRITIONAL HISTORY

• Malnutrition → Wernicke encephalopathy
• Vitamin deficiency

CLINICAL EXAMINATION 

1. GENERAL APPROACH 

Always follow ABCDE + Neurological prioritization

• Airway → patency, gag reflex
• Breathing → RR, pattern (Cheyne-Stokes, Kussmaul)
• Circulation → shock, arrhythmia
• Disability (Neuro) → core AMS exam
• Exposure → trauma, infection, toxidrome

2. LEVEL OF CONSCIOUSNESS (LOC)

A. Glasgow Coma Scale (GCS)

B. AVPU Scale 

• Alert
• Voice responsive
• Pain responsive
• Unresponsive

C. FOUR Score 

• Eye response
• Motor response
• Brainstem reflexes
• Respiration pattern

3. HIGHER MENTAL FUNCTIONS

Only if patient is arousable

A. Orientation

• Time, place, person

B. Attention

• Serial 7s
• Months backward

C. Memory

• Immediate, recent, remote

D. Language

• Aphasia → dominant hemisphere lesion

E. Thought content

• Delirium vs psychosis

4. CRANIAL NERVE EXAMINATION

Pupillary Examination

6

Key Findings

Brainstem Reflexes

1. Pupillary Light Reflex

• Midbrain function

2. Corneal Reflex

• CN V + CN VII

3. Oculocephalic Reflex (Doll’s eye)

• Absent → brainstem dysfunction

4. Oculovestibular Reflex (Cold calorics)

• Gold standard for brainstem assessment

5.  MOTOR SYSTEM EXAMINATION

A. Spontaneous Movements

• Purposeful vs non-purposeful
• Seizure activity

B. Response to Pain

C. Tone

• Hypotonia → metabolic coma
• Hypertonia → structural lesion

D. Reflexes

• Hyperreflexia → UMN lesion
• Hyporeflexia → metabolic/toxic

E. Plantar Reflex

• Extensor (Babinski) → UMN lesion

6.  SENSORY SYSTEM

(Usually limited in AMS)

• Response to pain (central vs peripheral)
• Asymmetry → focal lesion

7.  MENINGEAL SIGNS

Signs

• Neck stiffness
• Kernig’s Sign
• Brudzinski’s Sign

 Suggests:

• Meningitis
• Subarachnoid Hemorrhage

8.  RESPIRATORY PATTERNS

9. SIGNS OF TRAUMA / TOXIDROME

A. Trauma clues

• Scalp injury
• Battle sign
• Raccoon eyes

B. Toxidrome recognition

10. SYSTEMIC EXAMINATION 

A. Cardiovascular

• Arrhythmias → embolic stroke
• Shock

B. Respiratory

• Hypoxia → AMS

C. Abdomen

• Liver disease → hepatic encephalopathy

D. Skin

• Rash → meningococcemia
• Needle marks → drug abuse

11. RED FLAG FINDINGS 

• Unequal pupils
• Decerebrate posturing
• Absent brainstem reflexes
• GCS drop ≥2
• Seizures
• Signs of herniation

12.  LOCALIZATION APPROACH 

INVESTIGATIONS 

1. INITIAL BEDSIDE (These are life-saving)

• Capillary Blood Glucose (CBG) → MOST IMPORTANT
• Hypoglycemia (<60 mg/dL) → treat immediately
• Pulse oximetry
• ABG (with lactate)
• ECG
• Temperature

 3. LABORATORY INVESTIGATIONS 

A. BASIC METABOLIC PANEL (MANDATORY)

 B. ARTERIAL BLOOD GAS (ABG)

• Detect:
• Hypoxia → hypoxic encephalopathy
• Hypercapnia → CO₂ narcosis
• Metabolic acidosis → toxin, sepsis

Key clue:

• Respiratory acidosis → COPD / drug overdose
• High anion gap → toxin / sepsis / DKA

C. TOXICOLOGY SCREEN

Indications:

• Unknown cause
• Young patient
• Suspected overdose

Includes:

• Alcohol level
• Urine drug screen:
• Opioids
• Benzodiazepines
• Cocaine
• Amphetamines
• Serum:
• Paracetamol (VERY IMPORTANT – silent toxicity)
• Salicylates

 D. ENDOCRINE TESTS

 E. INFECTION WORKUP

• Blood cultures (before antibiotics)
• Urine routine + culture
• Procalcitonin (adjunct)
• Peripheral smear (malaria in India )

4. NEUROIMAGING 

 NON-CONTRAST CT BRAIN (FIRST-LINE)

Indications 

• Focal deficit
• Trauma
• Suspected stroke
• Papilledema
• Before lumbar puncture

 MRI BRAIN (SECOND-LINE / SUPERIOR)

Better for:

• Early ischemia
• Encephalitis
• Demyelination
• Posterior fossa lesions

 MRI sequences:

• DWI → stroke
• FLAIR → encephalitis
• SWI → microbleeds

 5. LUMBAR PUNCTURE (CSF ANALYSIS)

 Indications:

• Suspected meningitis / encephalitis
• Subarachnoid hemorrhage (if CT negative)
• Autoimmune encephalitis

 Contraindications (IMPORTANT):

• Raised ICP with mass lesion
• Focal deficit
• Papilledema

6. ELECTROENCEPHALOGRAPHY (EEG)

 Indications:

• Non-convulsive status epilepticus (NCSE) 
• Unexplained coma
• Suspected encephalopathy

 Findings:

• Triphasic waves → hepatic encephalopathy
• Epileptiform activity → seizures

7. ADVANCED / TARGETED INVESTIGATIONS

 A. AUTOIMMUNE / PARANEOPLASTIC

• Anti-NMDA receptor antibodies
• VGKC antibodies

 B. METABOLIC / GENETIC

• Serum lactate, ammonia (inborn errors)

 C. TOXIC ALCOHOL PANEL

• Methanol, ethylene glycol
• Osmolar gap >10–20

 D. CARDIAC CAUSES

• ECG → arrhythmia
• Troponin → MI
• Echo → embolic stroke source

 E. SPECIAL TESTS (CASE-BASED)

• Carboxyhemoglobin → CO poisoning
• Methemoglobin level
• Heavy metals (lead, arsenic)

 8. POCUS IN AMS

• Optic nerve sheath diameter → raised ICP
• Lung US → hypoxia cause
• Cardiac US → shock