Cerebellum surgical anatomy

Cerebellum is a part of CNS occurring in the posterior fossa, functioning in balance, speech, and eye movement.

1. SURESH BISHOKARMA, MS MCH RESIDENT, NEUROSURGERY NINAS CEREBELLUM

2. INTRODUCTION 3/15/18 CEREBELLUM SURGICAL ANATOMY

3. Cerebellum is divided into three lobes: anterior, posterior, and FN 3/15/18 CEREBELLUM SURGICAL ANATOMY L obes Flocculonodular lobe ( archicerebellum ): Oldest: Input from Vestibular nuclei:  balance and spatial orientation Anterior lobe ( paleocerebellum or spinocerebellum ): Evolution: input from dorsal columns of the spinal cord  and trigeminal nerve as well as from visual and auditory  system. Posterior lobe ( neocerebellum ): Fine 1. Primary fissure 2. Dorsolateral fissure

4. F issures and sulci divides cerebellum into 10 lobules 3/15/18 CEREBELLUM SURGICAL ANATOMY Lobules

5. In addition to the central vermal lobules, there are horizontal lobules that are also assigned Roman Numerals, but with the letter “H” before it, denoting it is a part of the hemispheres. Quadrangular lobule (H IV – V) - It is located anterior to the primary fissure. Simple lobule (H VI) - It is situated between the primary and the postlunate fissures. Superior semilunar lobule (H VII A) - The region runs from the postlunate fissure to the horizontal fissure. Inferior semilunar lobule (H VII B) - It continues from the horizontal fissure to the postlunate fissure on the inferior surface of the cerebellum. Biventer lobule (H VIII) - Its border is formed by the retrotonsillar fissure (anteriorly) and the postlunate fissure on the inferior surface (posteriorly). Cerebellar tonsils - They are a characteristic feature of the inferior surface of the posterior lobe. They are triangular structures that border the distal inferior vermis . 3/15/18 CEREBELLUM SURGICAL ANATOMY Horizontal Lobule

6. In terms of afferent and efferent connections, the cerebellum can also be organized into three parallel, sagittal zones: Vermian Paravermian Lateral 3/15/18 CEREBELLUM SURGICAL ANATOMY

7. The three cerebellar peduncles are attached to the cerebellum in the interval between the anterior and the flocculonodular lobes. 3/15/18 CEREBELLUM SURGICAL ANATOMY

8. ANATOMICAL AND PHYSIOLOGICAL FOUNDATIONS OF CEREBELLAR INFORMATION PROCESSING 3/15/18 CEREBELLUM SURGICAL ANATOMY A ll cerebellar cortical neurons, including the Purkinje cells, make inhibitory synaptic connections with their target neurons but granule cells. Layers:3 Molecular Purkinje granular Cells: 5 Stellate, Basket, Purkinje, Golgi, and Granule cells

9. Climbing fibres , which make direct excitatory contact with the Purkinje cells Mossy fibres , which terminate in the granular layer and make excitatory synaptic contacts mainly with granule cells. 3/15/18 CEREBELLUM SURGICAL ANATOMY

10. 3/15/18 CEREBELLUM SURGICAL ANATOMY INTRINSIC CIRCUIT Excitatory : Mossy fibers and the climbing fibers. This excitatory input is received by the Purkinje cells (directly and indirectly), Inhibitory: Output of purkinje cells to deep cerebellar nuclei The excitatory input to the Purkinje cells is further modified by the inhibitory influences of the modulating interneurons.

11. 3/15/18 CEREBELLUM SURGICAL ANATOMY Cerebellar nuclei Arrangement of the cortical gray matter and locations of the nuclei within the white matter

12. L argest lateral hemispheres . It resembles a crushed paper bag with its open end facing anteromedially . P artially encloses bundles of white matter  thatform  the  dentato rubrothalamic  and the  dentatoolivary tracts. V oluntary motor activity:   Timing , planning and inception. 3/15/18 CEREBELLUM SURGICAL ANATOMY Dentate Nucleus

13. M ost central pair of cerebellar nuclei Vermis just posterior to the roof of the 4th ventricle. Afferents: spinocerebellar  and  labyrinthine  afferents from the vermis , Efferent: project to the spinal cord (via the vestibular nuclei) and the ventral lateral thalamic nucleus  precentral gyrus (proximal and trunk muscles for maintenance of balance). 3/15/18 CEREBELLUM SURGICAL ANATOMY FASTIGIAL NUCLEUS

14. Lateral to the fastigial nucleus Interposed nucleus: the globose + emboliform nuclei   . Paravermis  Nuclei the   interpositorubrothalamic tract   ventral lateral thalamic nucleus and the red nucleus  precentral gyrus ( Brodmann 4 )  corticospinal tract to the distal muscles Distal flexor muscles via the  rubrospinal tract.. 3/15/18 CEREBELLUM SURGICAL ANATOMY Globose & Emboliform Nuclei GLOBOSE EMBOLIFORM

15. 3/15/18 CEREBELLUM SURGICAL ANATOMY Afferent connections Afferent cerebellar connections from brainstem and spinal cord Afferent cerebellar connections from Cortex Nuclei of pontine , reticular formation and vestibular nuclei give rise to mossy fibre while cells of inferior olivary nuclei give rise to climbing fibre .

16. 3/15/18 X: Crosses Midline = : Donot cross Efferent connections R ed nucleus Thalamus Vestibular complex Dentate nucleus SCP (X) Thalamus PMC CS Tract (X) C oordination of the ipsilateral body G lobose and Emboliform nuclei SCP (X) Red Nucleus Rubrospinal tract Facilitate flexor muscle tone Fastigial nuclei ICP (=) Lateral vestibular nuclei VS tract Facilitate extensor muscle tone DENTATO-THALAMIC VESTIBULO-SPINAL RUBRO THALAMIC

17. Principal afferent and efferent connections of the cerebellum.

18. PATHWAY PEDUNCLE LOCATION DIR ORIGIN DESTINATION ANTERIOR SPINOCEREBELLAR         SUPERIOR         MIDBRAIN   A MUSCLE SPINDLE, JOINTS, AND TENDON   CEREBELLUM   TECTOCEREBELLAR A SUPERIOR COLLICULUS GLOBOSE-EMBOLIFORM-RUBRAL   E CEREBELLUM   CONTRA: RED (N) IPSI: MOTOR (N) IN SP. CORD   DENTATO THALAMIC   E   CEREBELLUM CONTRA:VL AND MOTOR CORTEX THEN TO IPSI MOTOR (N) IN SP CORD. CORTICOPONTOCEREBELLAR     MIDDLE     PONS     A CORTEX     CEREBELLUM           CEREBRO-RETICULOCEREBELLAR A SENSORIMOTOR AREA CEREBRO-OLIVOCEREBELLAR           INFERIOR           MEDULLA   A CORTEX POSTERIOR SPINOCEREBELLAR A MUSCLE SPINDLE, JOINTS, AND TENDON CUNEOCEREBELLAR A MUSCLE SPINDLE, JOINTS, AND TENDON VESTIBULOCEREBELLAR A URTICLE, SACCULE AND SCC CEREBRORETICULOCEREBELLAR A CORTEX   RETICULOCEREBELLAR E CEREBELLUM   TO (N) OF RETI. FORM CEREBELLAR SURGICAL ANATOMY: CEREBELLAR PEDUNCLE: NINAS 2018 CEREBELLAR PEDUNCLES

19. Functional Anatomic Organization of Cerebellum Part Lobe Input Peduncle Nucleus Peduncle Target Function Vestibulocerebellum FN Ipsilateral vestibular nuclei and the vestibular ganglion. lateral geniculate nucleus, superior colliculi , and striate cortex. ICP Fastigial ICP Vestibular nucleus Axial muscle tone equilibrium. Head and eye coordination Spinocerebellar Vermis and intermediate hemisphere Dorsal and ventral spinocerebellar tracts. Auditory, visual, and vestibular system. Dorsal: ICP Ventral: MCP Vermian  Fastigial Brainstem reticular formation, the lateral vestibular nuclei, and the primary motor cortex Control of the medial descending systems, which regulate axial and proximal musculature. Intermediate  interposed nuclei  rubrospinal and lateral corticospinal tracts. SCP Rubrospinal and lateral corticospinal Lateral descending systems, which regulate the distal limb muscles. Pontocerebellar Lateral hemisphere contralateral cerebral cortex (especially that of the frontal and parietal lobes). MCP Dentate nuclues SCP Ventro -lateral nucleus of the thalamus “primary motor cortex, thus completing the corticopontine -thalamic-cortical loop precision in the control of rapid limb movements and with tasks requiring fine dexterity. CEREBELLAR SURGICAL ANATOMY: FUNCTIONAL DIVISION: NINAS 2018

20. 3/15/18 CEREBELLUM SURGICAL ANATOMY Cerebellar area and function : correlated symptoms with the lesion Anterior lobe of the cerebellum Truncal ataxia and hypotonia Posterior lobe Appendicular ataxia, Hypotonia and tremor Left cerebellar hemisphere Spatial and executive tasks Right cerebellar hemisphere Language tasks Cerebellar lobules V and VI that overlap the superior dentate nuclei Working memory and motor function, Inferior vermis that occupies the space between the two dentate nuclei Emotional processing and Normal neuro behavioural function Parts of lobules VI and VII that overlap the inferior part of the left dentate Nucleus Executive functions Parts of lobules VI and VII that overlap the inferior part of the right dentate nucleus Language Area lateral to the dentate in part of lobule VI lateral to dentate of the right Cerebellar hemisphere Language

21. 3/15/18 CEREBELLUM SURGICAL ANATOMY VASCULAR SUPPLY OF CEREBELLUM

22. They consist of the superior cerebellar veins and the inferior cerebellar veins. The superior cerebellar veins  the  straight sinus and the internal cerebral veins, transverse and superior petrosal sinuses. The inferior cerebellar veins  the  transverse, superior petrosal and occipital sinuses 3/15/18 CEREBELLUM SURGICAL ANATOMY VENOUS DRAINAGE

23. The clinical manifestations of cerebellar disease may be divided into three categories: The symptoms of cerebellar disease, The signs of midline cerebellar disease, and The signs of lateral (hemispheric) cerebellar disease. Midline and lateral zones BUT intermediate zone are associated with distinct abnormalities. 3/15/18 CEREBELLUM SURGICAL ANATOMY Clinical Manifestations of Cerebellar Disease

24. The symptoms of cerebellar disease are nonspecific. They include headache, nausea and vomiting, gait difficulty, and vertigo. 3/15/18 CEREBELLUM SURGICAL ANATOMY S ymptoms of cerebellar disease

25. A nterior and posterior vermis , the flocculonodular lobe, and the fastigial nuclei. Equilibrium Gait difficulty, Truncal imbalance, Abnormal head postures, and Ocular motor dysfunction. 3/15/18 CEREBELLUM SURGICAL ANATOMY SIGNS OF MIDLINE CEREBELLAR DISEASE

26. Truncal instability may be manifested during walking by a tendency to fall to the right, left, forward, or backward. While sitting, the patient may “lean or fall to one side. G ait ataxia: wider than normal base, unsteadiness and irregularity of steps, and lateral veering. 3/15/18 CEREBELLUM SURGICAL ANATOMY DISORDERS OF STANCE AND GAIT

27. M idline or lateral cerebellar lesions. 3/15/18 CEREBELLUM SURGICAL ANATOMY ABNORMAL POSTURES OF THE HEAD

28. Ocular motor dysfunction may occur in association with midline cerebellar lesions but is also associated with lesions in other parts of the cerebellum . The primary disorders of extraocular movements in midline cerebellar disease are nystagmus and ocular dysmetria . 3/15/18 CEREBELLUM SURGICAL ANATOMY OCULAR MOTOR DYSFUNCTION

29. 3/15/18 CEREBELLUM SURGICAL ANATOMY NYSTAGMUS Ocular Motor Dysfunction Gaze-evoked nystagmus occurs when an individual cannot maintain conjugate eye deviation away from the midposition . Conjugate lateral gaze is accompanied by a slow, involuntary drift of the eyes back to midposition , followed by a rapid corrective return of the eyes to the laterally located target. The result is a to-and-fro oscillation of the eyes involving a fast component in the direction of gaze and a slow component away. Rebound nystagmus: Specific for cerebellar disease. N ystagmus that changes direction after sustained lateral gaze or after refixation to the primary position . Optokinetic nystagmus Normal phenomenon optokinetic nystagmus become exaggerated, producing unusually large amplitudes of both the fast and the slow components.

30. Ocular dysmetria is defined as the conjugate overshoot of a target with voluntary saccades. The eyes appear to jerk back and forth because of repeated inaccuracies in saccadic movements intended to bring the target to the fovea. 3/15/18 CEREBELLUM SURGICAL ANATOMY OCULAR DYSMETRIA Ocular Motor Dysfunction

31. L ateral (hemispheric) zone of the cerebellum comprises the cerebellar hemisphere and the dentate and interposed nuclei of each side. (1) Hypotonia , ( 2) Dysarthria , ( 3) Limb ataxia, ( 4) Intention tremor, ( 5) Impaired check, and ( 6) Oculomotor disorders . 3/15/18 CEREBELLUM SURGICAL ANATOMY SIGNS OF LATERAL CEREBELLAR DISEASE

32. L ateral cerebellar lesions. It is best demonstrated by grasping the patient's forearms and shaking the relaxed wrists. Typically , the hypotonic limb is identified as the limb with more of a flail hand. In addition, examination of the patellar reflex in a hypotonic lower limb may demonstrate an increased duration and amplitude of swing. This pendular cerebellar reflex should be distinguished from clonus, due to corticospinal tract disease, which occurs at a more rapid rate than the pendular reflex . 3/15/18 CEREBELLUM SURGICAL ANATOMY HYPOTONIA SIGNS OF LATERAL CEREBELLAR DISEASE

33. The dysarthria of cerebellar disease is characterized by slow, labored, slurred, or garbled speech that may be mistaken, like cerebellar ataxia, as a manifestation of “alcohol intoxication. Comprehension and grammar remain intact . 3/15/18 CEREBELLUM SURGICAL ANATOMY DYSARTHRIA

34. Dysmetria consists of an error in trajectory and speed of movement. Finger nose test. L ateral cerebellar disease undershoot or overshoot (past-pointing) the target. To test the lower extremity: Slide the heel smoothly down the shin. Frequent deviations to one side or the other are indicative of dysmetria in that limb . D ecomposition Test for decomposition of movement : Finger nose test, dysdiadochokinesis . 3/15/18 CEREBELLUM SURGICAL ANATOMY LIMB ATAXIA Limb ataxia: Dysmetria and decomposition of movement

35. Intention tremor characteristically occurs during a sustained posture and from the beginning to the end of a movement . 3/15/18 CEREBELLUM SURGICAL ANATOMY INTENTION TREMOR

36. An impaired check response is characterized by the wide excursion of an affected limb following an involuntary displacement of the limb by an examiner. Rebound phenomenon 3/15/18 CEREBELLUM SURGICAL ANATOMY IMPAIRED CHECK

37. B oth lateral and midline cerebellar disorders As in midline cerebellar diseases: Gaze-evoked nystagmus, rebound nystagmus, ocular dysmetria , and optokinetic nystagmus. 3/15/18 CEREBELLUM SURGICAL ANATOMY OCULOMOTOR DISORDERS

38. Opsoclonus This disorder is characterized by constant, random, conjugate saccades of unequal amplitudes in all directions. Ocular flutter Ocular flutter is defined as rapid to-and-fro oscillations of the eyes. Ocular bobbing Ocular bobbing comprises intermittent (abrupt) downward displacement of the eyes, followed by a slow, synchronous return to the primary position. Horizontal eye movements are typically paralyzed . Ocular myoclonus Ocular myoclonus is defined as a rhythmic, pendular oscillation of the eyes that is associated with synchronous oscillation of the plate (palatal myoclonus). 3/15/18 CEREBELLUM SURGICAL ANATOMY LATERAL HEMISPHER Signs of Lateral (Hemispheric) Cerebellar Disease OCULOMOTOR DISORDERS

39. The mechanism behind cerebellar seizures or fits is linked to cerebellar herniation and brainstem compression and is not of cortical origin. Acute compression on the brainstem or acute increase in intracranial pressure T onic seizures to axial rigidity with motor automatism . sometimes clearly characterized by decerebrate or decorticate paroxysmal posturing. The EEG correlate is characterized by diffuse asynchronous slow waves of variable amplitude. Misrecognition of such entity may entail an incongruous therapeutic intervention in a life-threatening situation.  3/15/18 CEREBELLUM SURGICAL ANATOMY Cerebellar fits

40. Thank you  NATIONAL INSTITUTE OF NEUROLOGICAL AND ALLIED SCIENCES, BANSBARI, KATHMANDU CEREBELLUM - SURGICAL ANATOMY NATIONAL INSTITUTE OF NEUROLOGICAL AND ALLIED SCIENCES, BANSBARI, KATHMANDU