Cerebellar Disorders Presentatuin slide.pptx

This slide comprises of disorders of the cerebellum

1. Cerebellar Disorders Uchechi Ezem

2. Outline Introduction Anatomy Function Aetiology/Classification Clinical features Management Diagnosis Treatment

3. Introduction The cerebellum is situated in the posterior cranial fossa and is bordered superiorly by the tentorium cerebelli . It is the largest part of the hindbrain and lies posterior to the fourth ventricle, the pons, and the medulla oblongata. It is somewhat ovoid in shape and constricted in its median part. It consists of two cerebellar hemispheres joined by a narrow median vermis . It is connected to the posterior aspect of the brainstem by three symmetrical bundles of nerve fibers called the superior, middle, and inferior cerebellar peduncles. The cerebellum is divided into three main lobes: the anterior lobe, the middle lobe, and the flocculonodular lobe.

4. The cerebellum has 3 parts: Archicerebellum ( vestibulocerebellum ): It includes the flocculonodular lobe, which is located in the medial zone. The archicerebellum helps maintain equilibrium and coordinate eye, head, and neck movements; it is closely interconnected with the vestibular nuclei. Midline vermis ( paleocerebellum ): It helps coordinate trunk and leg movements. Vermis lesions result in abnormalities of stance and gait. Lateral hemispheres ( neocerebellum ): They control quick and finely coordinated limb movements, predominantly of the arms.

5. Consists of Internal white substance 4 pair of nuclei dentate nuclei (the largest and most lateral) emboliform nuclei globose nuclei fastigial nuclei (most medial) 3 cerebellar peduncles

6. Function of the cerebellum The cerebellum functions primarily and essentially to coordinate all reflex and voluntary muscular activity. It harmonizes muscle tone and maintains normal body posture. It permits voluntary movements, such as walking, to take place smoothly with precision and minimal effort. It must be understood that although the cerebellum plays an important role in skeletal muscle activity, it is not able to initiate muscle movement.

7. Classification/Aetiology Cerebellar disorders can be classified as Congenital, genetic or acquired. It can also be classified as acute, sub-acute and chronic cerebellar disorders The most common cause of cerebellar disorders is Alcoholic cerebellar degeneration One of the most common diseases affecting cerebellar function is acute alcohol poisoning. This occurs as the result of alcohol acting on GABA receptors on the cerebellar neurons.

8. Congenital cerebellar disorders These are generally malformations and they are almost always sporadic, often occurring as part of complex malformation syndromes (e.g., Dandy-Walker malformation) that affect other parts of the central nervous system (CNS). Malformations manifest early in life and are nonprogressive. Manifestations vary markedly depending on the structures involved; ataxia is usually present.

9. Genetic/Hereditary cerebellar disorders Hereditary ataxias may be autosomal recessive or autosomal dominant. Autosomal recessive ataxias include Friedreich ataxia, ataxia-telangiectasia, abetalipoproteinemia, ataxia with isolated vitamin E deficiency, and cerebrotendinous xanthomatosis .

10. Friedreich ataxia results from a gene mutation causing abnormal repetition of the DNA sequence GAA in the frataxin ( FXN) gene on the long arm of chromosome 9; the FXN gene codes for the mitochondrial protein frataxin . The GAA sequence is repeated 5 to 38 times within the FXN gene in people who do not have Friedreich ataxia; however, in people with Friedreich ataxia, the GAA sequence may be repeated 70 to > 1000 times. Inheritance is autosomal recessive. Decreased frataxin levels lead to mitochondrial iron overload and impaired mitochondrial function. In Friedreich ataxia, gait unsteadiness begins between ages 5 and 15; it is followed by upper-extremity ataxia, dysarthria, and paresis, particularly of the lower extremities. Mental function often declines. Tremor, if present, is slight. Reflexes and vibration and position senses are lost. Talipes equinovarus (clubfoot), scoliosis, and progressive cardiomyopathy are common. By their late 20s, patients may be confined to a wheelchair. Death, often due to arrhythmia or heart failure, usually occurs by middle age.

11. Acquired ataxia Acquired ataxias may result from nonhereditary neurodegenerative disorders (e.g., multiple system atrophy), systemic disorders, multiple sclerosis, cerebellar strokes, repeated traumatic brain injury, or toxin exposure, or they may be idiopathic. Systemic disorders include alcoholism (alcoholic cerebellar degeneration), thiamine deficiency, celiac disease, heatstroke, hypothyroidism, and vitamin E deficiency. Toxins that can cause cerebellar dysfunction include carbon monoxide, heavy metals, lithium, phenytoin, and certain solvents. Toxic levels of certain drugs (e.g., antiseizure drugs, sedatives in high doses) can cause cerebellar dysfunction and ataxia.

12. Acute cerebellar disorders Infarction, TIA Head trauma, oedema, haemorrhage Infections (acute post-viral cerebellitis ): Adults: VZV, EBV, Lyme disease, tertiary syphilis; , malaria, prion diseases (e.g., Creutzfeldt-Jakob disease) Children: VZV , coxsackie virus, parvovirus B19, HHV-6, hepatitis A, enteroviruses , measles , mumps , Lyme disease , etc. Medication, toxins, and poisons: barbiturates, benzodiazepines, heavy metals, and chemotherapy

13. Sub-acute and Chronic cerebellar disorders Alcoholism Intracranial tumours; (e.g., medulloblastoma ) Vitamin deficiencies: vitamin B12 deficiency, vitamin B1 deficiency (Wernicke encephalopathy) Paraneoplastic cerebellar degeneration Genetic: spinocerebellar ataxia, Friedrich ataxia, ataxia telangiectasia Multiple sclerosis Wilson disease (rare)

14. Aetiology Developmental causes: agenesis von Hippel-Lindau disease Arnold Chiari malformations Dandy Walker malformation Demyelinating causes: multiple sclerosis Degenerative causes: Friedreich's ataxia Louis Barr syndrome - ataxia telangiectasia Infectious causes: abscess formation acute cerebellaritis acute disseminated encephalomyelitis some variants of Guillain Barre syndrome Neoplastic causes: astrocytoma, medulloblastoma , haemangioblastoma metastasis

15. Metabolic causes: myxoedema alcohol / vitamin B1 deficiency Vascular causes: cerebellar haemorrhage cerebellar infarction Drug causes: anticonvulsants - phenytoin other sedatives - antipsychotics, benzodiazepines Toxins: Cyanide Heavy metals - Lead, methyl mercury, manganese, thallium, Podophyllin DDT, carbon tetrachloride Alcohol

16. Clinical features The clinical features vary depending on the underlying cause and severity of cerebellar injury. Symptoms manifest ipsilaterally to the site of the lesion. Symptoms and signs of acute lesions differ from those produced by chronic lesions. Acute lesions produce sudden, severe symptoms and signs, but there is considerable clinical evidence to show that patients can recover completely from large cerebellar injuries. Chronic lesions, such as slowly enlarging tumours, produce symptoms and signs that are much less severe than those of acute lesions.

17. Clinical features cont’d from unilateral hemisphere damage - ipsilateral signs: intention tremor - increases as limb reaches target dysdiadochokinesis - alternating hand, heel-knee-shin dysmetria - overshooting in finger-nose test ataxia of extremities - unsteadiness of gait towards side of lesion pendular reflexes - legs swing back and forth when knee jerk elicited rebound phenomena - outstretched arm swings excessively when displaced from damage to midline structures: disturbance of equilibrium - manifest as unsteadiness in walking: a drunken gait which is wide based or reeling on a narrow base sitting - truncal ataxia

18. Clinical features Vertigo: there is abnormal sensation of the world or room spinning or moving eye movements: nystagmus - in unilateral diseases, amplitude and rate increase when looking towards the diseased side; this is an inconsistent finding ocular dysmetria - overshoot when eyes voluntarily fixate speech: scanning dysarthria - especially with explosive speech - an inconsistent finding

19. LOCALIZING CEREBELLAR LESIONS Cerebellar lesion Signs Posterior ( Flocculo -nodular lobe; Archicerebellum ) Eye movement disorders: Nystagmus; Vestibuloocular reflex (VOR) Postural and gait dysfunction Midline ( Vermis ; paleocerebellum ) Truncal & gait ataxia Hemisphere ( Neocerebellum ) Limb ataxia: Dysmetria, Dysdiadochokinesis , "intention" tremor Dysarthria Hypotonia

20. Signs of Cerebellar Disorders Deficit Manifestation Vertigo Abnormal Sensation of motion Ataxia Reeling, wide-based gait Nystagmus Involuntary, rapid oscillation of the eyeballs in a horizontal, vertical, or rotary direction, with the fast component maximal toward the side of the cerebellar lesion Tremor Rhythmic, alternating, oscillatory movement of a limb as it approaches a target (intention tremor) or of proximal musculature when fixed posture or weight bearing is attempted (postural tremor); characterized by high amplitude and low frequency Dysarthria Inability to articulate words correctly, with slurring and inappropriate phrasing Scanning speech Slow enunciation with a tendency to hesitate at the beginning of a word or syllable Hypotonia Decreased muscle tone Decomposition of movement Inability to correctly sequence fine, coordinated acts, past pointing Dysdiadochokinesia Inability to perform rapid alternating movements Dysmetria Inability to control range of movement

21. History Onset Duration Progression History of trauma Family history Drug history Medical history History of metabolic disorders Social History – chronicity of alcohol consumption e.t.c

22. Physical examination General examination Examination to test for cerebellar ataxia Gait ataxia: abnormal wide-based and unsteady gait; irregular, uncoordinated activity of the muscles of pelvic girdle and/or lower limbs Romberg test: unable to perform Unterberger (Fukuda) stepping test: positive Truncal ataxia: Inability to sit upright and/or stand without support; most apparent in the sitting position Occurs due to damage to the cerebellar vermis Limb ataxia: Uncoordinated movements of the upper and lower extremities Occurs due to damage to the cerebellar hemispheres

23. Physical examination Test for dysmetria and tremor Finger to nose test Heel-knee-shin test Rebound test Tandem walking Past pointing Check for tremor in the hands by placing a piece of paper on the patient’s outstretched hands. Dysarthria: words are broken down into separate syllables and spoken with varying force.

24. Physical examination Test for hypotonia by assessing the tone of the muscles in the arms Knee jerk Test for dysdiadochokinesia Test for dysdiadochokinesis by showing the patient how to clap by alternating the palmar and dorsal surfaces of the hand. Ask them to do this as fast as possible and repeat the test with the other hand. Patient is unable to carry out rapidly alternating movement

25. Diagnosis Cerebellar syndromes are primarily a clinical diagnosis, and includes a thorough family history and search for acquired systemic disorders and is based especially on the evaluation of posture, gait, and movement.

26. Differential Diagnoses Haemorrhagic and Ischaemic stroke Acute cerebellitis Thiamine deficiency( Werniecke’s encephalopathy) Cerebellar tumors

27. Investigation FBC E/U/Cr Vit . B12 and B1 levels Thyroid function test Neuroimaging (MRI) to rule out infarction, haemorrhage, tumour, oedema. Genetic testing is indicated if family history is suggestive or if other diagnostic tests are negative or inconclusive.

28. Treatment Treatment of the cause if possible Usually only supportive Some systemic disorders (e.g., hypothyroidism, celiac disease) and toxin exposure can be treated. Occasionally, surgery for structural lesions (tumour, hydrocephalus) is beneficial. However, treatment is usually only supportive (e.g., exercises to improve balance, posture, and coordination; devices to help with walking, eating, and other daily activities).

29. References Cerebellar syndromes – Knowledge for medical students and physicians. Available from: https://www.amboss.com/us/knowledge/Cerebellar_syndromes Cerebellar Disorders - Neurologic Disorders - MSD Manual Professional Edition. Available from: https://www.msdmanuals.com/professional/neurologic-disorders/movement-and-cerebellar-disorders/cerebellar-disorders Snell’s neuroanatomy Harrison’s Principle of internal medicine 20 th edition https://neupsykey.com/cerebellar-disorders-differential-diagnosis/