Disorders of the Extrapyramidal System

Abstract

The chapter begins with an overview of human motor system control of both voluntary and involuntary movements. Movement disorders or extrapyramidal disorders are characterized by abnormal movements in conscious patients. Damage to or presumed dysfunction of the basal ganglia and their brainstem and cerebellar connections is implicated in the etiology of these diseases. Movement disorders are characterized by either excessive (hyperkinetic) or reduced (hypokinetic) activity. Hyperkinetic movements are characterized by tremor, chorea, dystonia, athetosis, ballismus, myoclonus, and tics. The reader can view videos of many hyperkinetic movement disorders. The chapter then covers in detail essential tremor, Parkinson’s disease, and Huntington’s disease with attention to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

A 59-year-old man makes an appointment with a neurologist for tremor. He has noted difficulty with a tremor in both of his hands. It interferes with drinking from a cup and his handwriting has become very difficult for him to read. He also finds it embarrassing when he is trying to sign a check at the store. He has started having a glass of wine before going out to dinner as his tremor does not seem to bother him as much after drinking the wine. His neurological exam reveals normal language and cranial nerve function. He has normal strength and tone. He does have a high-frequency, small amplitude tremor in both hands that is seen on posture and with action. There is no tremor at rest. His gait is normal. On handwriting examination, he has a tremulous spiral. After history and examination, he is diagnosed with essential tremor. As the patient finds the symptoms intrusive, he is started on symptomatic medications to reduce the tremor.

Video Legend

This video shows a 66 year-old woman with Essential Tremor

Segment 1: Motor Exam

• Low amplitude, high frequency postural/action tremor

• Absence of rest tremor

• Absence of bradykinesia

• Head/Neck tremor present

Segment 2: Cerebellar Exam

• No intention tremor

Segment 3: Handwriting Example

• Tremor on handwriting and Archimedes spiral

This video shows a 70 year-old man with Parkinson disease

Segment 1: Cranial Nerve Exam

• Hypometric saccades

• Hypophonia

Segment 2: Motor Exam

• Bradykinesia

• No tremor with DBS

Segment 3: Gait Exam

• Shortened stride length

• En bloc turn