5. • 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
6. • 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
7. 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.
8. • Neuropsychological components of conscious brain state are
organized in a hierarchical architecture.
Arousal
Memory
Mood-emotion
Awareness
Attention Intention
12. • 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
13. • 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
16. • 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’.
17. • 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
18. • 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.
20. • 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
24. • 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
25. • 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
26.
27. MRI showing bilateral paramedian thalamic infarction.
Shetty A C et al. Age Ageing 2009;38:350-351
29. • Disorders of consciousness could belong to one of the following
two categories, functionally & anatomically;
i. Diffuse functional impairment of both hemispheres due to direct injury
ii. Selective impairment of midline or paramedian upper brainstem &
basal forebrain regions
• Three categories of patients;
i. Significant structural injury with poor predictors for death/disability
ii. Patients with early steady recovery with good predictors
iii. Patients with mixture of structural/functional disturbance
30. • 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
31. • 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
33. • 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
39. • Extraocular Muscle function
A. 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’
40. 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
41.
42. • 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
43.
44. • 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
45.
46.
47.
48. • 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
51. • 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
53. • 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
54. • 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
55. • 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
56. • 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
58. • 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
