Disorders of the Brainstem and Cerebellum

Abstract

The chapter begins with discussion of anatomy and functions of the brainstem (mesencephalon, pons, and medulla) and cerebellum. No other part of the central nervous system is packed with so many critical axon tracts and nuclei. Main brainstem functions are as follows: to provide transit and processing nuclei for ascending and descending pathways that convey signals to and from the cerebellum, cerebrum, and spinal cord; to integrate functions such as consciousness, muscle tone, posture, and normal autonomic functions; and to house cranial nerves 3–10. The cerebellum occupies only 10 % of the brain volume but contains more neurons than the entire rest of the brain. Lesions in the brainstem often manifest as cerebellar, somatosensory and motor symptoms plus cranial nerve dysfunction. Damage to the cerebellum often results in errors in smooth motor movements. The chapter ends with a discussion of central pontine myelinolysis, lateral medullary syndrome or Wallenberg’s syndrome, and spinocerebellar atrophies with attention to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

A 44-year-old woman with a history of alcoholism is brought to the emergency room by her husband. He reports that over the past 2 days, she has been confused and sleepy. Her examination showed jaundice and lethargy. On laboratory examination, her serum sodium was found to be 124 mmol/L. Correction of her serum sodium commenced but her mental status worsened requiring admission to the intensive care unit. She developed spastic quadriparesis and had only limited ability to move her eyes up and down. MRI of the brain revealed hyperintensity in the pons suggestive of central pontine myelinolysis. She was supported with mechanical ventilation and nutrition. Despite this support, she passed away within a month of her initial presentation.

Video Legend

This video shows a 67 year-old woman with Multiple System Atrophy-Type Cerebellar

Segment 1: Cranial Nerve Exam

• Saccadic intrusions into fixation

• Dysmetric and slow saccades

• Impaired vestibulo-ocular reflex

• Scanning dysarthria

Segment 2: Cerebellar Exam

• Dysmetria on finger-to-nose

• Overshooting target on finger chase

• Dysmetria on heel-to-shin

• Limb rebound

Segment 3: Gait Exam

• Ataxic gait requiring use of walker