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By
Dr Manah Chandra Changmai
Thalamus is a part of diencephalon
Diecephalon divided into 4 regions
Thalamus
Hypothalamus
Epithalamus
Ventral thalamus(or subthalamus)
Diencephalon
Thalamus
Thalamus Large mass of grey matter,lies immediatelylateral to third ventricle
The thalamus is an ovoid nuclear mass, c.4cm long, which borders the dorsal part of third ventricle
Two polesAnterior pole(or end) -Lies behind the interventricular foramenPosterior pole(or end) -Also called PULVINAR -Lies just above and lateral to superior colliculus. Thalamus
Anterior pole
Posterior pole or pulvinar
Thalamus
Superior colliculus
Interventricular foramina
Thalamus
Superior(dorsal) surface -The superior (dorsal) surface of the thalamus is covered by a thin layer of white matter, the stratum zonale
-It extends laterally from the line of reflection of the ependyma (taenia thalami), and forms the roof of the third ventricle
-This curved surface is separated from the overlying body of the fornix by the choroid fissure with the tela choroidea within it.
-More laterally it forms part of the floor of the lateral ventricle.
-related laterally to caudate nucleus
-Seperated from caudate nucleus stria terminalis and thalamostriate vein.
Superior surface
Superior surface
Inferior surface
Medial surface
Surfaces of the thalamus
The medial surface of the thalamus is the superior (dorsal) part of the lateral wall of the third ventricle.
It is usually connected to the contralateral thalamus by an interthalamic adhesion behind the interventricular foramina.
The boundary with the hypothalamus is marked by an indistinct hypothalamic sulcus, which curves from the upper end of the cerebral aqueduct to the interventricular foramen.
The thalamus is continuous with the midbrain tegmentum, the subthalamus and the hypothalamus
Medial surface
The medial surface
Medial surface of thalamus
Hypothalamus
Midbrain tegmentum
Inferior surface of the tegmentum is relatedto hypothalamus anteriorly and to ventralthalamus posteriorly.
The ventral thalamus seperates the thalamusfrom tegmentum of midbrain
Inferior surface of thalamus
Internally, the thalamus is divided into anterior, medial and lateral nuclear groups by a vertical Y-shaped sheet of white matter, the internal medullary lamina
Nuclei of the anterior part.Anterior nucleus.
Nuclei in the medial partLargest nuclei among them medial dorsal nucleus.
Internal structure of the thalamus
Thalamus consists of mainly of grey matter
Superior surface is covered by a thin layer ofwhite matter called stratum zonale
Lateral surface is covered by a similar layer called externalmedullary layer.
Nuclei in the lateral part
Ventral group Lateral group
Ventral anterior nucleus
Ventral lateral nucleus OrVentral intermediate nucleus
Ventral posterior nucleus
Lateral dorsal nucleus
Lateral posteriornucleus
Pulvinar
Other thalamic nuclei
Intralaminar nucleiEmbedded within the internal medullaryLamina
Midline nucleiScattered cells between medial part of thethalamus and ependyma of third ventricle.
Medial and lateral geniculate bodiesNow included under the thalamus.
Connections of the thalamus
Afferent impulses from large number ofSubcortical centres converge to the thalamus.
Visual and aduditory impulses reach the lateralAnd medial geniculate bodies.
Sensation of taste are conveyed to the thalamus Through solitariothalamic fibres
Thalamus does not receive direct olfactory impulsesThey probably reach through amygdaloid complex.
Thalamus receive profuse connections from all partOf cerebral cortex,cerebellum and corpus striatum.
Thalamus is there fore regarded as integrating centreWhere information of all sources is brought together.
The information from thalamus is projected to wholeOf the cerebral cortex through thalamo-cortical projection.
Thalamocortical fibres form large bundles known as Thalamic radiations or thalamic radiation.
Thalamic radiations
Superior thalamic radiation (dorsal )
Posterior thalamic radiations ( caudal )
Ventral thalamic radiation
Anteriorthalamic radiations
Superior thalamic radiations
Posterior thalamic radiation
Thalamus
Connection of ventral group of nuclei
Most important connection of thalamus are from ventral posteriornucleus
cerebral cortex (somatosensory area,3 1 2)
ventral posterior nucleus
medial part lateral part
Trigeminothalamic tractSolitariothalamic tract
Medial leminiscusSpinothalamic tract
cerebral cortex
premotor and supplementary motor area
Area 4
ventral lateral nucleus
Anterior part Medial part Posterior part
From globus pallidus
From substantianigra
FromCerebellar nucleiVestibular nucleiSpinal cord
Ventral lateral nucleus
cerebral cortexGyrus cinguli
Parahippocampal gyrus
Parietal lobe
Prefrontal & orbitofrontal
Temporal Occipital lobe
Lateral dorsal
Lateral posterior pulvinar
Superior colliculus& Pretectal area
Retina
Connection of lateral group of nucleuses
Medial and lateral geniculate bodies are ovalCollection of grey matter
Situated below the posterior part of thalamus.
Traditionally under metathalamus,functionallyUnder thalamus.
The medial geniculate bodies-Relay station of the auditory pathway.-Medial geniculate body recieves fibres of lateral leminiscus.-Fibres arising in the medial geniculate bodies constitute the acoustic radiation.
Medial geniculate body
Acoustic area of cerebral cortex
Medial geniculate body
pulvinar
Inferior colliculus
Superior olivary nucleus
Opposite superior olivary nucleus
Inferior brachium
Lateral leminiscus
Connection of medial geniculate body
Lateral geniculate body
Relay station for visual pathway
Recieves fibres from retinae of both the eyes
Efferent fibres arising in the body constitute optic radiation.
Sections through lateral geniculate body shows partially split six lamellae seperated by nerve fibres.
Lateral geniculate body also recieves fibres from primary visual cortex.,superior colliculus,and from the reticular formation of pons and medulla.
Lateral geniculate body
Lateral geniculate body
Raphe nuclei
Locus coeruleus
Other areas in pons & medulla
Reticular formation
Pulvinar
Retina Ipsilateral & Contralateral
Visual areas of cerebral cortex
Superior colliculus
Connections of lateral geniculate body
Blood supply of thalamus
Perforating branches of the posterior cerebral artery
Posteromedial group(thalamo-perforating arteries) supplymedial and anterior part.
Posterolateral group ( thalamo-geniculate branches) supplyposterior and lateral part of thalamus.
Also recieves branches from posterior communicatinganterior choroidal,posterior choroidal and middle cerebralartery.
Thalamic syndrome
Thalamic syndrome (or thalamic pain syndrome) is a condition that can be associated with inadequate blood supply from the posterior cerebral artery.
Rare neurological disorder in which the body becomes hypersensitive to pain as a result of damage to the thalamus, a part of the brain that affects sensation
Primary symptoms are pain and loss of sensation, usually in the face, arms, and/or legs.
Pain or discomfort may be felt[1] after being mildly touched or even in the absence of a stimulus.
The pain associated with thalamic syndrome may be made worse by exposure to heat or cold and by emotional distress. Sometimes, this may include even such emotions as those brought on by listening to music.
It is also known as "Dejerine-Roussy disease", after Joseph Jules Dejerine and Gustave Roussy
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