THALAMUS AND BASAL
GANGLIA
THALAMUS
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A group of nuclei in the wall of 3rd ventricle
Largest structure in the diencephalon
Bounderies
-medial: third ventricle
-lateral: posterior limb of internal capsule
-dorsolateral: terminal sulcus
-inferior: hypothalamic sulcus
Cont’d
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Internal medullary lamina divides thalamus
into ant., medial and lateral areas
-ant. area: anterior nuclear group
-medial area: dorsomedial and medline nuclei
-lateral nuclei: dorsal and ventral tier
Cont’d
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Ventral tier
Dorsal tier
-vent. Anterior
-dorsolateral
-vent. Lateral
-lateral posterior
-vent. Posterior
-pulvinar
Others:
-intralaminar nuclei
-reticular nuclei
Four regions from diagnostic
standpoint
1.The midline, intralaminar, reticular nuclei
-nonspecific thalamic nuclei
-mediate general cortical alerting responses
-projections from midbrain RF, fibers from
spinothalamic tract
-project to midbrain and specific thalamic nuc
-bilateral lesions cause impairment of
conciousness
Cont’d
2.The medial﴾ dorsomedial ﴿ and ant. thalamic n.
-important role in memory and emotions
-connected with hyypoth. and the “limbic lobe”
-lesions associated with memory and executive
function loss
3.The dorsolateral and post. nuclear groups
-modulates occipito-temporo-parietal cortical
attention
-facilitates visual attention and the cortical attention needed for language
related sensory tasks in the L. hemisphere and visuospatial tasks in the R..
cont’d
4.ventral lateral and basal nuclear groups
-for processing and relay to the cortex of
sensory information and sensorimotor control
-ventral posterior nuclear group
-medial geniculate body
-lateral geniculate body
VASCULAR SUPPLY
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From posterior cerebral and post.
Communicating arteries
Polar arteries
Paramedian thalamomesencephalic arteries
Thalamogeniculate pedicle
Posteromedial choroidal arteries
Posterolateral choroidal arteries
LOCALISATION OF ISCHEMIC
THALAMIC LESIONS
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Paramedian territory
-due to embolic occlusion of top of basilar a. Or
local atheroma
-clinical triad of somnolent apathy , memory loss and
abnormalities of vertical gaze
Thalamogeniculate territory
-ischemia around VP,VL nuc., subthalamic n.
-hemianesthesia, transient slight hemiparesis
,hemiataxia, choreoathetoid mov’ts, paroxyxmal
pain,homonymous hemianpopia
Cont’d
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Tuberothalamic territory
-due to thalamopolar a. lesions
results in neuropsychological dysfunction
Posterior choroidal a. territory
-homonymous quadrantanopsia
-hemisensory loss with mild hemiparesis
-transcortical aphasia
Thalamic hemorrhages
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One of the common sites of hypertensive h’ge
Prominent sensory deficits
Contralat. Hemiplegia or hemiparesis
Aphasia after h’ge into dominant thalamus
Homonymous visual field defects
Ocular dysfunction
Dejerine-Roussy syndrome
Prognosis depends on amount and site of bleeding
-ant. and dorsal types: usually benign
-posteromed. and posterolat. types: poor prognosis
BASAL GANGLIA
COMPONENTS
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No generally accepted defination
Considered to include
1.corpus striatum﴾ neostriatum﴿
-putamen and caudate nucleus
2.claustrum
3.substantia nigra: pars compacta and pars reticularis
4.globus pallides
5. subthalamic nucleus
Cont’d
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Play a major role in the control of posture and
movement
Straitum- receptive component
Globus pallidus – its internal seg’t, output str.
Subthalamic – input from cer. cortex and reciprocal
connection with G.P
Substantia nigra- pars compacta: contain dopamine
-pars reticulata :continuation of
internal segment of globus pallidus
connections
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Striatum receives three main inputs
-excitatory input from cerebral cortex
-excitatory input from intralaminar thalamic
nuclei
-modulatory input from substantia nigra PC.
Striatal efferents
-inhibitory GABAergic cells that project to
the G.p and substantia nigra
Cont’d
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Internal segment of G.P
-project to three main targets
-to thalamus
-tosuperior colliculus
-pedenculopontine nuclei of reticular form
Output of B.G affects both corticospinal and
brainstem motor pathways
Lesions of B.G
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Subthalamic nuc.- contralat. Hemiballismuss
Caudate nucleus- contralat. Choreoathetosis
Globus pallidus-unilat.: contralat.hemidystonia ,hemiparkin.
or tremor
-bilat.:dystonia ,parkisonism abulia, akinesia
Substantia nigra -parkinsonism
Cont’d
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Two main types of disorders of B.G
·hyperkinetic﴾ dyskinetic ﴿ disorders
-when dopaminergic mechs.exagerated
·hypokinetic ﴾akinetic ﴿disorders
-when dopaminergic mechs. impaired
Dyskinesias
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Chorea
Tardive and orofacial dyskinesias
Ballismus
Athetosis, dystonia, torticollis
Myoclonus
Tics
tremor
Hypokinetic disorders
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Parkinsonism
Corticobasal degeneration
Progressive supranuclear palsy
Multiple systems atrophy