5256 · 5 Cerebellum
Hypotonia and hyporeflexia. In an acute lesion of the cerebellar hemisphere, the muscular resistance to passive movement is diminished, and abnormal postures (e. g., of the hand) may result. The intrinsic muscle reflexes are also diminished in the hypotonic muscles.
Scanning dysarthria and dysarthrophonia. These manifestations arise mainly as a result of paravermian lesions and reflect impaired synergy of the musculature of speech. The patient speaks slowly and haltingly, with poor articulation, and with an abnormal, unvarying stress on each syllable.
Cerebellar Disorders
Cerebellar Ischemia and Hemorrhage
Arterial blood reaches the cerebellum through the three cerebellar arteries: the superior cerebellar, anterior inferior cerebellar, and posterior inferior cerebellar arteries. The origin and anatomical course of these arteries and the typical clinical manifestations of occlusions of each of them are presented in Chapter 11 on p. 427ff. The typical manifestations of cerebellar hemorrhage are presented on p. 480f.
Cerebellar Tumors
Cerebellar tumors are only rarely confined to a single subdivision of the cerebellum.
Benign cerebellar tumors (such as pilocytic astrocytoma) may be problematic in that they often grow quite large before producing symptoms, because of the plasticity of the cerebellum. Papilledema, an indirect sign of an intracranial mass, may be lacking for a long time, particularly in adults; it is present in about 75% of affected children. In most cases (90%), cerebellar tumors manifest themselves initially with occipitocervical headache and nausea and vomiting on an empty stomach (dry heaves). A forced head tilt is a clinical sign of impending herniation of the cerebellar tonsils through the foramen magnum.
Medulloblastoma is a malignant tumor that preferentially affects children and adolescents and accounts for one-third of all brain tumors in this age group (8% of all brain tumors regardless of age). It often arises from the roof of the fourth ventricle and then grows into the vermian portion of the flocculonodular lobe, possibly metastasizing to other regions of the brain and spinal cord
Baehr, Duus' Topical Diagnosis in Neurology © 2005 Thieme
All rights reserved. Usage subject to terms and conditions of license.
Cerebellar Disorders · 257 |
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Fig. 5.8 Medulloblastoma, seen in T1-weighted MR images after intravenous administration of contrast material. a A large, markedly and homogeneously contrast-enhancing tumor is seen in the superior portion of the vermis. The tumor compresses the fourth ventricle and causes occlusive hydrocephalus, as manifested by the enlarged temporal horns of the lateral ventricles. b The coronal image shows the origin of the tumor from the superior vermis and reveals marked dilatation of the lateral ventricles.
through the cerebrospinal fluid (drop metastases). Because this type of tumor often begins in the vestibulocerebellum, its typical initial sign is dysequilibrium: the affected child has a broad-based, swaying, and staggering gait. Further cerebellar manifestations including ataxia, dysmetria, asynergia, adiadochokinesia, and intention tremor gradually arise as the tumor grows further and begins to affect the lateral portions of the cerebellum (the hemispheres). In advanced stages of tumor growth, blockage of the fourth ventricle or of the cerebral aqueduct causes occlusive hydrocephalus, with clinical signs of intracranial hypertension (Fig. 5.8).
Astrocytoma and hemangioblastoma. Similar manifestations are produced by pilocytic astrocytoma, a further characteristic type of posterior fossa tumor arising near the midline. On the other hand, hemangioblastoma in the setting of von HippelLindau disease and cystic astrocytoma tend to arise in the cerebellar hemispheres and, therefore, to produce appendicular ataxia and gazeevoked nystagmus as their typical manifestations.
Baehr, Duus' Topical Diagnosis in Neurology © 2005 Thieme
All rights reserved. Usage subject to terms and conditions of license.
