Altered ConsciousnessApproach to Patient Assessment

Dr Mukhtar

PG Neurosurgery

HMC, Peshawar

Road Map

• Basic Taxonomy• Discussion of;

• Coma• Vegetative State• Minimal Conscious State (MCS)• Akinetic Mutism

• Physiologic & Anatomic Considerations• Guide to Prognosis• Recent Developments & their applications

Introduction

Consciousness

Content Arousal

Cognitive + Affective responsesInteraction with environment

• Altered consciousness is the most common clinical finding encountered by the neurosurgeon

• Clinical syndromes associated with brain injury include;• Coma• Vegetative State (VS)• Minimally Conscious State (MCS)• Akinetic Mutism and others

• Knowledge of forebrain arousal mechanisms;• formulating probabilities & recovery time frames• Spectral knowledge of Coma, VS or MCS

• The aim of this presentation is;• NOT to present the details of numerous diagnoses;• Rather;

• To conceptualize the neurologic disorders of consciousness• And formulation of an organized & physiological approach towards a

patient with altered consciousness

• Approach to patients with altered consciousness require;• Foundation of the basic principles underlying maintenance of normal

wakeful state• Knowledge of the forebrain arousal mechanisms• Effects of various types of neurologic injury on consciousness

Taxonomy

Schiff & Plum’s working definition for normal wakeful conscious state

• At its least, normal human consciousness consists of a serially time-ordered, organised, restricted and reflective awareness of self and the environment. Moreover, it is an experience of graded complexity and quantity.

• Neuropsychological components of conscious brain state are organized in a hierarchical architecture.

Arousal

Attention

Memory Mood-emotion Awareness

Coma

• Total absence of patterned behavioural arousal or EEG features of sleep-wake architecture

• By definition the term implies that;• The state has endured for at least 1 to six hours

• It is a transient condition and does not persist beyond 10 to 14 days; unless complicated by concurrent systemic illness

• Motionless patient in eyes-closed state without spontaneous eye opening periods

• Deep forceful stimulation may produce facial grimace or withdrawal reflexes from the spine

• Lack of localisation and absence of organised sequence of movements

• Lack of primitive reflexes

Vegetative state

• first described in 1940 by Ernst Kretschmer who called it apallic syndrome

• The term was introduced by Jennett & Plum in 1972 and defined it as;“The clinical syndrome of ‘persistent vegetative state’, identified by dissociation of an apparent recovery of behavioural wakeful arousal associated with periods of eye opening alternating with eye closure and where the patient does not show any evidence of awareness of self or environment”

• Earlier use of the term implied a VS lasting longer than 30 days as ‘Persistent Vegetative State’.

• VS typically follows an initial coma produced by the initial insult to brain

• Two most common causes of VS;• Severe TBI• Cardiac Arrest

• Loss of thalamic neurons and thalamocortical connections especially the central thalamic intralaminar nuclei and components of thalamic association nuclei

• Bilateral injuries to these areas produce coma

• Cardiac arrest is associated with widespread neocortical neuronal death as compared to Diffuse Axonal Injury due to trauma (64% vs 11%)

• No significant brainstem damage on autopsy, which implies that VS is primarily a disorder of corticothalamic system integration

• Stereotyped limbic responses, such as grimaces are preserved.

Minimal Conscious State

• First level of behavioural recovery beyond VS

• Definition• a condition of severely altered consciousness in which minimal but definite

behavioural evidence of self or environmental awareness is demonstrated

• consistent and sustained visual tracking or fixation

• Intermittent spoken language responses, verbal output & gestures

• Diagnostic Criteria

Akinetic Mutism

• MCS patients who functionally can communicate, however, demonstrate a severe reduction in spontaneous behaviour or extremely slowed interactive responses

• Highly attentive, vigilant patient with wide opening eyes and deliberate visual tracking and no other spontaneous behaviour

• Injury patterns; bilateral anterior medical regions of cerebral cortex, bilateral caudate injury, bilateral central thalamic lesions, basal forebrain injuries, mesencephalic reticular formation damage

• Two types; Apathetic AM and Herpathic AM Or Mesencephalic and Frontal AM

• Classic finding after Anterior communicating artery aneurysm rupture

• Slow Syndrome; severe memory loss, slowed behavioural responses, listless, apathetic appearance

MRI showing bilateral paramedian thalamic infarction.

Shetty A C et al. Age Ageing 2009;38:350-351

Anatomic and Physiologic ConsiderationsBasis of assessment strategies

• Disorders of consciousness could belong to one of the following two categories, functionally & anatomically;i. Diffuse functional impairment of both hemispheres due to direct injuryii. Selective impairment of midline or paramedian upper brainstem &

basal forebrain regions

• Three categories of patients;i. Significant structural injury with poor predictors for death/disabilityii. Patients with early steady recovery with good predictorsiii. Patients with mixture of structural/functional disturbance

• Category 1 patients:• Bedside exam with clinical judgment• Large size prospective studies supporting predictors for death or

permanent VS (loss of motor responses/pupillary and corneal reflexes)

• Category 2 patients:• No realistic characterisation exist, in terms of stages and time frame• Early achievement of consciousness/high cortical functions

• Category 3 patients:• Significant diagnostic/prognostic challenge• Known structural injury to critical brain areas but without indicators of

poor outcome or permanence of their disability• At present no reliable measures/clinical judgment for better

predictability of their condition

• Establishment of exact diagnosis (Coma, VS, MCS)

• Most common transitional signs from VS to MCS are visual fixation and visual tracking

Approach to the Patientclinical pearls

• GCS;

• technically, a scale for measuring impaired consciousness• ‘Coma’, simply implies ‘unresponsiveness’• 90% patients below GCS 8 & none above GCS 9 signifies

the above definition of COMA• Therefore, GCS 8 is the operational definition of coma• Slight modification for children

• Pseudocoma

• Locked-in Syndrome• Psychiatric• Neuromuscular weakness

• ABC…• Initial baseline investigations

• RFTs, Electrolytes, CBC, ABGs• Toxicology, calcium, ammonia, AEDs level (as appropriate)

• Initial resuscitation (if the cause is obvious)• I/V Glucose bolus• Naloxone• Flumazenil• Thiamine

• Core Neurologic Exam• Respiratory rate & Pattern

• Cheyne-Stokes• Hyperventilation• Cluster breathing• Apneustic• Ataxic

• Pupils• The light reflex is useful in distinguishing metabolic from structural

coma• Metabolic causes of fixed dilated pupils include glutethionoid

toxicity, anoxic encephalopathy, anticholinergic

• Pinpoint pupils in narcotics overdosage

• Unequal size (anisocoria)• Fixed & dilated pupil

(Oculomotor palsy, Herniation syndrome)• Horner syndrome

• Bilateral pupillary defects• Pinpoint with very little reaction (pontine lesion)

• Bilateral fixed & dilated (7 – 10 mm)• Subtotal medullary damage/hypothermia/anoxia

• Midposition fixed (4 - 6 mm)• Extensive midbrain damage

• Extraocular Muscle functionA. Bilateral conjugate deviation

• Frontal lobe lesion (towards affected side)

• Pontine lesion (away from the lesion)

• Medial thalamic haemorrhage (wrong way gaze)

• As a rule supratentorial lesions cause deviation towards the lesion side while infratentorial lesions cause deviation away from the lesion side except in ‘wrong way gaze’

B. Unilateral outward deviation on side of larger pupil• Uncal herniation

C. Unilateral inward deviation (VI nerve palsy)

D. Skew deviation• III or IV nerve/nucleus lesion• Infratentorial lesion

• Manoeuvres to test brain stem

• Oculovestibular reflex (Ice Water Caloric)• Patient with intact brainstem deviate towards side of

the caloric• Oculocephalic reflex (doll’s eyes) has similar objective

but dangerous for C-spine if it is not cleared

• One mnemonic used to remember the FAST direction of nystagmus is COWS.

• COWS: Cold Opposite, Warm Same.

• Cold water = FAST phase of nystagmus to the side Opposite from the cold water filled ear

• Warm water = FAST phase of nystagmus to the Same side as the warm water filled ear

• In other words: Contralateral when cold is applied and ipsilateral when warm is applied

• No response in case of;• NMBAs, toxins• Metabolic cause• Brain death• Massive infratentorial lesion

• Asymmetric in case of infratentorial lesion• Nystagmus without tonic deviation diagnostic of

psychogenic coma• Contralateral eye adduction failure: Internuclear

ophthalmoplegia

• Motor• Babinski

• Appropriate: corticospinal tracts/cortex intact• Asymmetric: supratentorial lesion• Inconsistent/Variable: Seizures, Psychogenic• Symmetric: metabolic, asterixis, tremor

• Hyporeflexia: consider myxoedema coma

• Patterns:• Decorticate Large cortical or subcortical lesion• Decerebrate Brainstem injury at or below midbrain• Arms flexed, legs flaccid: pontine lesion• Arms flaccid, legs normal: anoxic injury (man in the barrel syndrome)

• Ciliospinal reflexes• Pupillary dilatation to cutaneous noxious stimuli)• Tests integrity of sympathetic pathways• Bilateral present: metabolic• Unilaterally present: lesion III if on side of larger pupil• Bilaterally absent: not diagnostic

Formulating PrognosisA Brief Guide

• Outcome is always dependent upon the clinical findings, time from the injury and cause of injury

• Disorders of consciousness are transitional states with increasingly long time windows • (i.e., coma to VS, VS to MCS)

• Step 1: Locate the patient temporally in the natural history of a disorder• (e.g., VS in the first month after a severe traumatic brain injury is not

comparable to VS at 6 months or 1 year)

• Step 2: Identify the cause

• Coma is an inherently grave illness associated with very high mortality; • 40% to 50% of patients in a coma after brain trauma• 54% to 88% of patients comatose after cardiac arrest

• Outcome always depends upon negative clinical predictors• Bilateral loss of pupillary and corneal reflexes

• Recovery from TBI coma is higher than coma after cardiac arrest

• Prognosis of VS depends on injury mechanism

• Non-traumatic VS for 3 months is permanent VS

• These timeframes are longer for traumatic VS, • usually longer than 1 year to declare permanence

• Transitions from one state to another are not equally distributed across a continuum

• Prognosis in MCS is least well characterised because this diagnostic category is relatively new

• Studies suggest that significant recovery after 1 year may occur in some patients

• Patients with MCS show faster changes in rate of recovery during the first year post-injury

Emerging role of Neuroimaging

• The use of functional MRI for differentiation of various states of altered consciousness

• Ruling out false positive VS or MCS patients

• Limitations of this technology include;• Cost, availability, expertise, legal implications• Obtaining reliable fMRI data from severely brain injured

patient• Misinterpretation and lack of generalisation due to limited

patient data

Thanks!