Disconnection syndrome

Disconnection Syndrome

Dr Gulab Soni

White matter connection

3 types of white matter fibre:

1) Commissural fibre: interhemispheric

2) Association fibre: intrahemispheric

3) Projection fibre- Vertical

Horizontal

Disconnection syndrome:Introduction

• Defined as symptoms and sign, which are arises due to white matter disconnection

• 1965 - Norman Geschwind, US neurologist

• Usually two types-

1) Interhemispheric disconnection syndrome: due to involvement of commissural fibres

2) Intrahemispheric disconnection syndrome: due to association fibres involvement

Disconnection syndromeFibre type Tract involved Symptoms

Association Arcuate fasciculus Conduction aphasia, ideomotor apraxia

Inferior longitudinal fasciculus

Visual object agnosiaPure alexiaProsopagnosia (B/L)

Commissural Corpus callosum Left hand apraxia, left hand agraphia, pure alexia etc

Projection Corticospinal tract Locked in syndrome, hemiparesis

Apraxia

Visual object agnosia

Inability to recognize object by sight

• Based on lesion:

a) Lateral occipital cortex (cortical): apperceptivevisual agnosia

b) Associative fibre connections (transcortical): associative visual agnosia-disconnection syndrome

DORSAL STREAM-VISUALY GUIDED ACTION

VISUAL INFORMATION

VENTRAL STREAM-VISUAL RECOGNITION

Visual object Agnosia

Alexia

Acquired inability to read

1) Alexia without agraphia /pure alexia / pure word blindness/visual verbal agnosia -disconnection syndrome

2) Alexia with agraphia- lesion at angular gyrus

3) Third alexia/ alexic agraphia- seen with brocas aphasia

Pure Alexia

Conduction aphasia

Conduction aphasia

• The lesions of conduction aphasia usually involve either the superior temporal or inferior parietal region.

1) Conduction aphasia plus limb apraxia: parietal lesions

2) Conduction aphasia without apraxia: temporal lesions

Callosal Disconnection Syndrome

Verbal Disconnection Motor Disconnection

Left visual anomia Crossed optic ataxia

Left hemialexia Left unilateral motor apraxia

Left auditory anomia Agraphia of the left hand

Left tactile anomia Right unilateral construnctionalapraxia

Right olfactory anomia Alien hand syndrome

Mainly due to-Posterior callosal lesion Mainly due to-Anterior callosal lesion

A) Verbal disconnection disorders

• Verbal output is exclusively sub served by the left hemisphere

• So in callosal lesion patient have difficulty in communicating from right hemisphere

1. Left visual anomia

• Image seen in right visual field (left hemisphere) are normally named or described, while those shown in the left hemi field (right hemisphere) cannot.

• Lesion site: Posterior and dorsal portion of splenium

2. Left hemialexia

• Special case of anomia for words shown in the left visual field, patient unable to report aloud or write down those presented on the left side

• Lesion site: Ventral and anterior portion of splenium

3. Left auditory anomia

• Repetition of verbal material (syllables, wordsand numbers) or naming of auditory stimuli(sound and voices) are normal when presented toeach ear separately- due to the bilateralprojection of cortical auditory pathway

• Bilateral simultaneous stimulation of both ear,results in deficit from left ear i.e right hemisphere

• Lesion site: Posterior inferior trunk/isthmus

4. Left tactile anomia

• Patient can describe and name objects palpated with the right hand (without vision)but not with the left hand

• Also k/a pseudoastereognosis

• Lesion site: posterior trunk

5. Right olfactory anomia

• Odors presented to right nostril (right hemisphere) are not named, while those presented to left nostril (left hemisphere) are—olfactory inputs project ipsilaterally.

• No anosmia: patient winces in response to unpleasant odours

B) Motor disconnection disorders

• Difficulty in coordinating bimanual gesture due to lack of sensory motor transfer, ex-difficulty in tie shoelaces in absence visual inspection

• Rapid alternating movement of both hand also impaired, ex-hand clapping/tapping

• Lesion: anterior corpus callosum

1. Right unilateral constunctionalapraxia

• Difficulty in drawing and constructive abilities when using right hand

• Due to disconnection of the left motor cortex from right hemisphere visuospatial skills

2. Alien hand syndrome

• “Feeling that one limb is foreign or “has a will of its own,” together with observable involuntary motor activity

• Depending upon the site of lesion, 3 types of alien hand syndrome described

Alien hand syndrome

Frontal variant Callosal variant Sensory variant

Clinical features Reflexive grasping, groping and compulsive manipulation of tools

Intermanualconflict

Levitation

Lesion site Medial prefrontal cortex Anterior corpus callosum

Parietal cortex

Affected side of hand

Dominant hand Nondominanthand

Nondominant hand

Associated finding Transcortical motor aphasia,

Sensory ataxia,Optic ataxia,neglect

Cause ACA territory strokeCallosal surgery in epilepsyHead injury

CBGDPosterior cortical atrophy (AD)

Geschwind’s disconnection syndromesDisconnections between sensory areas and limbic cortex

Disconnections between sensory areas and Wernicke’sarea

Disconnections between sensory areas and motor cortex

Disconnection between the hemispheres

Pain asymbolia (no response to pain in the presence of normal tactile discriminatory function)

Tactile aphasia/anomia/agnosia: (the inability to name a held object in the presence of preserved speech and naming in other sense modalities

Conduction aphasia/central aphasia: disconnections of Broca’s area fromWernicke’s area

Callosal disconnectionsyndrome

Verbal learning impairment examples- autism, schizophrenia

Pure word deafness(auditory verbal agnosia): inability to understand spoken words in the presence of preserved hearing

Apraxia: disconnections of the hand motorcortex from posterior sensory area

Pure word blindness: (visual verbal agnosia or alexia)

Thank-u

References:• Adams and victors-text book of neurology, 10th edition

• Bradleys text book of neurology, 6th edi

• Stroke Syndromes, 3ed . By Louis R. Caplan, Jan van Gijn

• Marco Catani and Dominic H. The rises and falls of disconnection syndromes. Brain (2005), 128, 2224–2239

• Developmental Neuropsychology (Otfried Spreen, Anthony H. Risser, Dorothy Edgell)

• The American Psychiatric Publishing Textbook of Geriatric Neuropsychiatry (Norman L. Foster)

• Limb kinetic apraxia: localises lesion at premotor cortex or adjacent centrum semiovale/corona radiata

• Ideomotor apraxia: not follow command, pantomime and imitation of object, how they are used but when object given to patient the demonstrate there use

• Ideational apraxia: deficit in the execution of a goal-directed sequence of movements of a tool

• Alien hand phenomenon: severe form of sympathetic apraxia, characterized by additional features of motor disinhibition on the left hand

• Dressing and construction apraxia: bilateral (or right-sided) dorsal parietal lobe lesions, denotes disturbance in spatial orientation

• In callosal apraxia when lesion extends towards medially it may be associated with trancortical aphasia