basal nuclei

basal nuclei radioanatomy and related pathologies

1. Basal Nuclei Dr. Md. Suzon Islam FCPS Part II Trainee Dept. of Radiology & Imaging Dhaka Medical College and Hospital

2. Contents: Gray matter vs white matter What is basal nuclei Parts of basal ganglia and their relations Modalities to detect abnormalities Related pathology

3. Neuron: Cell body: composed of mainly protein. Devoid of myelination. Axon: presence of myelin sheath which is composed of lipids (70%–85%) and proteins (15%–30%) Grey matter is made up of nerve cell bodies White matter is made up of fibers/ axons

4. Grey matter In the CNS, the cell bodies of neurons are often grouped together in discrete areas termed nuclei, or they may form more extensive layers or masses of cells; collectively they constitute the grey matter. Cortical : The grey matter surrounding the cerebrum Subcortical/deep: basal nuclei , thalamus, hypothalamus etc.

5. Basal Nuclei The basal nuclei are a group of grey matter nuclei in the deep aspects of the brain that is interconnected with the cerebral cortex, thalami and brainstem.

6. Present Nomenclature Basal ganglia Basal nuclei V ery widely used term 'basal ganglia' is actually a misnomer . A ganglion is a collection of nerve cell bodies outside of the central nervous system. A nucleus is a collection of nerve cell bodies inside of the central nervous system. T he official term for the basal ganglia is basal nuclei as it is part of CNS

7. Parts of basal nuclei Anatomically it is composed mainly of three paired nuclei which can be subdivided into two groups: Caudate nucleus Lentiform nucleus: Composed of two nuclei > Putamen > Globus pallidus Functionally, two additional nuclei are also part of the basal ganglia: Subthalamic nuclei Substantia nigra

8. Terms related to basal nuclei Corpus striatum Neostriatum/ Stritum Paleostriatum

9. Corpus striatum: Caudate nucleus, Putamen, Globus pallidus Paleostriatum: Globus pallidus Neostriatum/Striatum: It further consists of: Dorsal striatum: The dorsal striatum is the main component of the basal ganglia. It is composed of Caudate nucleus Putamen Ventral striatum: The ventral striatum is considered part of the limbic system. This is composed of Nucleus accumbens Olfactory tubercle

10. Caudate nucleus The caudate nucleus is C shaped highly curved and lies within the concavity of the lateral ventricle. It is composed of three parts. H ead : head projects into the floor of the anterior horn of lateral ventricle. Body : body lies along the body of the lateral ventricle T ail : The tail of caudate nucleus extends under the internal capsule behind the thalamus forming a roof with the inferior horn of lateral ventricle and ends in the amygdaloid nucleus Caudo-thalamic groove separates caudate nucleus from thalamus Superior to the caudate nucleus lies the corpus callosum.

11. Lentiform nucleus This is shaped like a biconvex lens. It is made up of Larger lateral putamen Smaller medial globus pallidus . It is separated from the head of the caudate nucleus anteriorly and from the thalamus posteriorly by the internal capsule . A thin layer of white matter on its lateral surface is called the external capsule

12. Coronal section through anterior horn of lateral ventricle

13. Coronal section through body of lateral ventricle

14. Axial section of basal ganglia and thalamus

15. Vascular Supply of basal nuclei Mostly lenticulostriate arteries branch of middle cerebral artery

16. Modalities to detect abnormalities of the basal ganglia CT scan MRI USG (infants) PET scan

17. CT Basal nuclei is hyperdense to white matter, isodense with cortex o Punctate or dense globular Ca++ common. Usually symmetric, in globus pallidus internus. Common in middle-aged, older patients

18. Axial CT scan of basal ganglia and thalamus

19. Axial CECT scan of basal ganglia and thalamus

20. Coronal CT scan of basal ganglia

21. Ultrasound: Basal ganglia is isoechoic in head ultrasound. Hyperechoic basal ganglia would indicate oedema, ischemia or hemorrhage.

22. Coronal section of the fetal head USG

23. Coronal section of the fetal head USG

24. MRI At MR imaging, the caudate nucleus and putamen are isointense relative to the cortical gray matter with all pulse sequences and do not enhance after contrast material injection. The globus pallidus demonstrates less signal intensity than the adjacent putamen on T2-weighted MR imaging due to iron deposition and is relatively T1-hyperintense due to myelination . When calcification exceeds 30%, there is signal loss in all sequences

25. Axial T1 MR

26. Axial T1 MR

27. Coronal T1 MR

28. Axial T2 MR

29. Axial T2 MR

30. T2 T1 T2

31. PET scan: With PET and SPECT techniques, the whole integrative dopaminergic network of neurons can be studied which plays an important role in differential diagnostics. Parkinson's disease, Tourette's syndrome, dystonia, Huntington's chorea and Wilson's disease can be evaluated with this technique

32. with predominant, homogeneous and symmetric activity in the basal ganglia similar to the normal subject with a greater activity in the posterior region of the putamen nucleus (C) marked reduction is observed in the posterior region of the putamen in both hemispheres.

33. Imaging Recommendations: MR (axial, coronal) best general imaging NECT for Ca++

34. Related pathology Radiologically important symptoms regarding basal nuclei are abnormalities of movement, muscle tone & posture • Putamen is most common location affected by hypertensive hemorrhage • GP is most sensitive area of brain to hypoxia (in addition to hippocampus) • BG is common location for strokes, particularly lacunar infarcts & hypertensive hemorrhages Basal ganglia calcification Lacunar infarcts Parkinson disease Huntington disease Hallervorden-Spatz syndrome Central pontine myelinolysis Gliomatosis cerebri Hypertensive haemorrhage

35. Basal ganglia calcification Symmetrical calcifications in the globus pallidus, pulvinar thalami found in CT scanning. T1-weighted MRI revealed small patchy hypersignals in the globus pallidus and pulvinar thalami T2-weighted MRI revealed small patchy hyposignals in the globus pallidus

36. Left basal ganglia hemorrhage Axial non contrast CT image demonstrates a hyperdense focus centered on the globus pallidus on the left with a faint rim of low attenuation. Findings are characteristic of a basal ganglia haemorrhage .

37. "Disappearing basal ganglia" sign indicates right basal ganglia infarct pCT was performed. Cerebral blood volume (CBV) shows markedly reduced blood volume in the right basal ganglia

38. Lacunar infarct Axial T2WI shows multiple bilateral rounded and irregular hyperintensities in the basal ganglia and deep cerebral white matter. FLAIR MR shows multiple hyperintensities in both hemispheres. Some small subcortical lesions are also present. Some lesions demonstrate acute restriction ſt. DWI is helpful in distinguishing acute from chronic lacunar infarcts.

39. Intercaudate distance increases in Huntington disease

40. Bibliography Diagnostic and Surgical Imaging Anatomy Brain, Head & Neck, Spine by Harnsberger , Osborn, Macdonald, Ross Ryan Anatomy for Diagnostic Imaging Osborn’s Brain imaging, pathology, and anatomy Grays Anatomy www.radiopaedia.org/articles/basal-ganglia

41. Thank You