2. White matter connection
3 types of white matter fibre:
1) Commissural fibre: interhemispheric
2) Association fibre: intrahemispheric
3) Projection fibre- Vertical
Horizontal
3.
4.
5.
6.
7.
8. 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
9.
10. Disconnection syndrome
Fibre type Tract involved Symptoms
Association Arcuate fasciculus Conduction aphasia,
ideomotor apraxia
Inferior longitudinal
fasciculus
Visual object agnosia
Pure alexia
Prosopagnosia (B/L)
Commissural Corpus callosum Left hand apraxia, left hand
agraphia, pure alexia etc
Projection Corticospinal tract Locked in syndrome,
hemiparesis
15. 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
18. 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
19. 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 construnctional
apraxia
Right olfactory anomia Alien hand syndrome
Mainly due to-Posterior callosal lesion Mainly due to-Anterior callosal lesion
20. 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
21. 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
22. 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
23. 3. Left auditory anomia
• Repetition of verbal material (syllables, words
and numbers) or naming of auditory stimuli
(sound and voices) are normal when presented to
each ear separately- due to the bilateral
projection 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
24. 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
25. 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
26. 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
27. 1. Right unilateral constunctional
apraxia
• Difficulty in drawing and constructive abilities
when using right hand
• Due to disconnection of the left motor cortex
from right hemisphere visuospatial skills
28. 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
29. Alien hand syndrome
Frontal variant Callosal variant Sensory variant
Clinical features Reflexive grasping,
groping and compulsive
manipulation of tools
Intermanual
conflict
Levitation
Lesion site Medial prefrontal cortex Anterior corpus
callosum
Parietal cortex
Affected side of
hand
Dominant hand Nondominant
hand
Nondominant hand
Associated finding Transcortical motor
aphasia,
Sensory ataxia,
Optic ataxia,
neglect
Cause ACA territory stroke
Callosal surgery in epilepsy
Head injury
CBGD
Posterior cortical
atrophy (AD)
30. Geschwind’s disconnection syndromes
Disconnections between
sensory areas and limbic
cortex
Disconnections between
sensory areas and Wernicke’s
area
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 from
Wernicke’s area
Callosal disconnection
syndrome
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 motor
cortex from posterior
sensory area
Pure word blindness: (visual
verbal agnosia or alexia)
31.
32. 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)
33. • 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
34. • 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
