Disorders of higher mental function

Disorders of higher mental function
Amnesia, Aphasia,
Apraxia, Agnosia
Delirium & Dementia

Lateralization of brain function
 Brain- two cerebral hemispheres, connected
by corpus callosum
 95% of R-handed & 80% of L-handed people
have L hemisphere dominance for language
 Lateralization-
 L hemisphere- exact calculation;
language- grammar, vocabulary, literal
 R hemisphere- approximate calculation;
language- intonation/accentuation,
prosody, pragmatic, contextual

Amnesia
 Defect in memory
 Organic or functional
 Forms-
 Anterograde-inability to memorize new things
 Retrograde- inability to recall pre-existing memories
 Types-
 Immediate- few seconds- in delirium
 Recent- minutes-days- in dementia/delirium
 Remote- months-years- usually intact, till late dementia
 Causes- delirium, post-traumatic, dementia

Types of amnesia
 Delirium- loss of all memory with
loss of orientation to time, place, person
 Post-traumatic- transient or permanent,
related to degree of injury
 Transient global amnesia- impaired recent memory,
due to hippocampal dysfunction, complete recovery
within a day
 Blackout- anterograde amnesia following binge
drinking
 Korsakoff’s syndrome- due to thiamine-B1 deficiency,
severe memory loss with ataxia & confabulation
 Drug-induced- midazolam & propofol- medical use,
recent memory loss of procedural events

Disorders of language
 Language- a system of signs-symbols or gestures-
for encoding & decoding information
 Aphasia- defective processing of linguistic
information- receptive and/or expressive
 Speech- a modality to convey language
 Dysarthria- defective articulation- pure motor,mainly
consonants; due to neurological injury affecting
V,VII,IX,X,XII cranial n.
 Dysphonia- impaired sound production- mainly
vowels, due to defect in larynx/vocal cords

Aphasia
 Causes- stroke, trauma, tumor, degenerative
 Manifestations-
 Inability to comprehend
 Inability to speak spontaneously & fluently
 Inability to form words or neologisms
 Inability to read/write
 Inability to name
 Inability to repeat/persistent repetition

Testing for aphasia
 Spontaneous speech- fluency, volume,
initiation, pauses
 Naming- name objects
 Repetition
 Comprehension- point to objects named
 Reading
 Writing

Types of aphasia
 Wernicke’s- temporal lobe
 Defect in comprehension, fluent nonsensical speech
 Broca’s- frontal lobe
 Defect in expression- non-fluent, effortful, slow speech
 Associated right face/arm hemiparesis
 Conduction- arcuate fasciculus/auditory cortex
 Poor repetition & naming, good comprehension, fluent speech
 Global- Wernicke’s + Broca’s
 Pure word deafness- impaired auditory comprehension
 Pure word blindness- impaired reading comprehension

Apraxia- motor
Loss of ability to carry out learned
purposeful movements,
despite having desire & physical
ability to do so

Types of apraxia
 Ideomotor- inability to carry out a motor
command, limb or buccofacial
 Ideational- inability to create a plan for or an
idea of a specific movement
 Constructional- inability to draw or construct
simple configurations
 Speech- impaired ability to speak
 Gait- impaired coordination of leg movements

Agnosia- sensory
Loss of ability to recognize-
object/person/shape/sound/smell-
without any sensory or memory loss

Types of agnosia
 Alexia- inability to recognize text
 Amusia- inability to recognize/appreciate music
 Apperceptive- unable to distinguish visual shapes,
can’t copy shapes
 Integrative- can identify elements/parts, but not
integrate them into whole
 Prosopagnosia- inability to recognize familiar faces
 Astereognosia- inability to recognize objects by
touch, based on its texture, size or weight
 Visual- inability to recognize objects by seeing them

Delirium & Dementia
Disorders of
higher mental function
Delirium-acute, Dementia-chronic

Delirium
 An acute confusional state, with
fluctuating course
 A common disorder in hospitalised
patients, specially elderly/in ICU
 Manifestation-
 Attention deficits, abnormal behaviour, altered
sensorium, incoherent speech
 Cognitive defects- memory, orientation, planning
 Changed sleep pattern, hallucination/delusion

Causes
 Majority outside brain
 High-grade fever, infection in elderly
 Hypoxia- ACS, CVA, pneumonia etc.
 Hypoglycemia, acute renal/hepatic impairment
 Electrolyte abnormality, specially Na, Ca
 Alcohol/benzodiazepine withdrawl
 Illicit drug abuse, poisoning, psychotropic drugs
 Head injury
 Brain disorders- stroke, bleed, tumor, raised ICP

Management
 Dx-
 Clinical presentation
 Ix- CBC, RBS, Cr, SGPT, Na, Ca, ABG, ECG, CxR
 CT scan/MRI- rule in/out primary brain disease
 Rx-
 Treat underlying cause
 Supportive treatment- oxygenation, hydration, nutrition
 Treat fever, pain, constipation
 Optimize drugs

Dementia
 A chronic- >6 months- symptom complex
 Usually progressive & incurable
 Affects cognition- memory, attention,
language, problem-solving
 Depression, anxiety, agitation are common
 Causes-
 Fixed cognitive- one time insult- trauma, hypoxia, stroke
 Slowly progressive- neurodegenerative- Alzhiemer’s, vascular,
hypothyroidism, Wilson’s, normal pressure hydrocephalus
 Rapidly progressive- Prion diseases- Creutzfeldt-Jakob disease

Management
 Dx-
 Cognitive testing- mini mental state examination- MMSE-
orientation, registration, attention, calculation, recall, language
 PET scan- for Alzheimer’s disease
 CT/MRI- to detect structural cause
 CBC, Cr, SGPT, TSH- for a treatable cause
 Rx- mainly supportive
 Drugs- anticholinesterase inhibitors- tacrine, donepezil,
galantamine, rivastigmine or NMDA blocker- memantine
 Antidepressants or anxiolytics- as required
 Px- progressive, incurable, life-span reduced

Disorders of higher mental function

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Disorders of higher mental function