APPROACH TO THE PATIENT: Movement Disorders
Divided into akinetic rigid forms, with muscle rigidity and slowness of movement, and hyperkinetic forms, with involuntary movements. In both types, preservation of strength is the rule. Most movement disorders arise from disruption of basal ganglia circuits; common causes are degenerative diseases (hereditary and idiopathic), drug induced, organ system failure, CNS infection, and ischemia. Clinical features of the various movement disorders are summarized below.
Inability to initiate changes in activity or perform ordinary volitional movements rapidly and easily. There is a slowness of movement and a paucity of automatic motions such as eye blinking and arm swinging while walking. Usually due to Parkinson’s disease or other causes of parkinsonism (Chap. 182).
Rhythmic oscillation of a part of the body due to intermittent muscle contractions, usually involving the distal limbs and less commonly the head, tongue, or jaw. A coarse tremor at rest, 4–5 beats/s, is usually due to Parkinson’s disease. A fine postural tremor of 8–10 beats/s may be an exaggeration of normal physiologic tremor or indicate familial essential tremor (ET). An intention tremor, most pronounced during voluntary movement toward a target, is found with cerebellar pathway disease.
This is the most common movement disorder. The tremor of ET must be distinguished from early Parkinson’s disease (Table 54-1). The pathophysiology of ET is unknown. Approximately 50% of cases have a positive family history with autosomal dominant inheritance; linkage studies have implicated several loci, and recently a mutation in the fused in sarcoma (FUS) gene, previously implicated in familial ALS, was identified in one ET family. The oligodendrocyte gene LINGO1 has been suggested in association studies, especially in early onset familial cases. Many pts with ET have mild symptoms and require no treatment.
TABLE 54-1ADVANCED EXAMINATION PEARLS: DIFFERENTIATING ESSENTIAL TREMOR FROM PARKINSONIAN TREMOR |Favorite Table|Download (.pdf) TABLE 54-1ADVANCED EXAMINATION PEARLS: DIFFERENTIATING ESSENTIAL TREMOR FROM PARKINSONIAN TREMOR
| ||Essential Tremor ||Parkinsonian Tremor |
|Speed ||5–10 Hz ||4–6 Hz |
|Symmetry ||Bilateral ||Usually asymmetric |
|Most common component ||Postural ||Rest |
|Other parkinsonian symptoms ||Absent ||Present |
|Helped with alcohol ||Usually ||Rarely |
|Family history ||Present often ||Usually absent |
When activities of daily living such as eating and writing are impaired, therapy with propranolol (20–120 mg/d) or primidone (12.5–750 mg/d) leads to benefit in 50% of pts.
Surgical therapies targeting the thalamus may be effective in refractory cases.
Consists of sustained or repetitive involuntary muscle contractions, frequently causing twisting movements and abnormal posture. May be generalized or focal; >300,000 cases in the United States.
Focal dystonias are common and include blepharospasm of the eyelids; spasmodic dysphonia involving the vocal cords; oromandibular dystonia of the face, lips, tongue, ...