Paralysis and Movement Disorders

PARALYSIS OR WEAKNESS

GENERAL CONSIDERATIONS 

The loss of power or control of voluntary

muscle is usually described by pts as “weakness” or as some difficulty

that can be interpreted as “loss of dexterity.” The diagnostic approach begins

by determining which part of the nervous system is involved. It is important to

distinguish weakness arising from disorders of upper motor neurons (i.e.,motor

neurons in the cerebral cortex and their axons that descend through the subcortical

white matter,internal capsule, brainstem,and spinal cord) from disorders

of the motor unit (i.e.,lower motor neurons in the ventral horn of the spinal

cord and their axons in the spinal roots and peripheral nerves,neuromuscular

junction,and skeletal muscle). In general:

• Upper motor neuron dysfunction: increased muscle tone (spasticity),brisk

deep tendon reflexes,and Babinski sign.

• Lower motor neuron dysfunction: reduced muscle tone,diminished reflexes,

and muscle atrophy.

Table 41-1 summarizes patterns with lesions of different parts of the nervous

system. Table 41-2 lists common causes of weakness by the primary site of

pathology.

EVALUATION The history should focus on the tempo of development

of weakness,presence of sensory and other neurologic symptoms,medication

history,predisposing medical conditions, and family history. The physical exam

aids in localization (Table 41-1). An algorithm for the initial workup of weakness

is shown in Fig. 41-1.

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.

BRADYKINESIA Inability to initiate changes in activity or perform ordinary

volitional movements rapidly and easily. There is a slowness of move Common Causes of Weakness

UPPER MOTOR NEURON

Cortex: ischemia; hemorrhage; intrinsic mass lesion (primary or metastatic

cancer,abscess); extrinsic mass lesion (subdural hematoma); degenerative

(amyotrophic lateral sclerosis)

Subcortical white matter/internal capsule: ischemia; hemorrhage; intrinsic

mass lesion (primary or metastatic cancer,abscess); immunologic (multiple

sclerosis); infectious (progressive multifocal leukoencephalopathy)

Brainstem: ischemia; immunologic (multiple sclerosis)

Spinal cord: extrinsic compression (cervical spondylosis,metastatic cancer,

epidural abscess); immunologic (multiple sclerosis,transverse myelitis); infectious

(AIDS-associated myelopathy,HTLV-1 –associated myelopathy,

tabes dorsalis); nutritional deficiency (subacute combined degeneration)

MOTOR UNIT

Spinal motor neuron: degenerative (amyotrophic lateral sclerosis); infectious

(poliomyelitis)

Spinal root: compressive (degenerative disc disease); immunologic (Guillain-

Barre´ syndrome); infectious (AIDS-associated polyradiculopathy,Lyme disease)

Peripheral nerve: metabolic (diabetes mellitus,uremia, porphyria); toxic (ethanol,

heavy metals, many drugs,diphtheria); nutritional (B12 deficiency); inflammatory

(polyarteritis nodosa); hereditary (Charcot-Marie-Tooth); immunologic

(paraneoplastic,paraproteinemia); infectious (AIDS-associated

polyneuropathies and mononeuritis multiplex); compressive (entrapment)

Neuromuscular junction: immunologic (myasthenia gravis); toxic (botulism,

aminoglycosides)

Muscle: inflammatory (polymyositis,inclusion body myositis); degenerative

(muscular dystrophy); toxic (glucocorticoids,ethanol, AZT); infectious

(trichinosis); metabolic (hypothyroid,periodic paralyses); congenital (central

core disease)

ment and a paucity of automatic motions such as eye blinking and arm swinging

while walking. Usually due to Parkinson’s disease.

TREMOR Rhythmic oscillation of a part of the body,usually involving

the distal limbs and less commonly the head,tongue, and 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; the latter often responds to propranolol or primidone.

An intention tremor,most pronounced during voluntary movement towards

a target,is found with cerebellar pathway disease.

ASTERIXIS Brief,arrhythmic interruptions of sustained voluntary muscle

contraction,usually observed as a brief lapse of posture of wrists in dorsiflexion

with arms outstretched. This “liver flap” may be seen in any encephalopathy

related to drug intoxication,organ system failure,or CNS infection.

Therapy is correction of underlying disorder.

MYOCLONUS Rapid,brief,irregular movements that are usually multifocal.

Like asterixis,often indicates a diffuse encephalopathy. Following cardiac

arrest,diffuse cerebral hypoxia may produce multifocal myoclonus. Clonazepam,

valproate, or baclofen may be effective.

DYSTONIA Involuntary,sustained deviation in posture about one or

more joints. Postures attained are often bizarre,with forceful extensions and

twisting. Dystonias may be generalized or focal (e.g.,spasmodic torticollis,

blepharospasm). Symptoms may respond to high doses of anticholinergics,benzodiazepines, baclofen, and anticonvulsants. Local injection of botulinum toxin is effective in certain focal dystonias.

CHOREOATHETOSIS A combination of chorea (rapid,jerky movements)

and athetosis (slow writhing movements). The two usually exist together,

though one may be more prominent. Choreic movements are the predominant

involuntary movements in rheumatic (Sydenham’s) chorea and Huntington’s

disease. Athetosis is prominent in some forms of cerebral palsy. Chronic neuroleptic use may lead to tardive dyskinesia,in which choreoathetotic movements are usually restricted to the buccal,lingual,and mandibular areas. Benzodiazepines, reserpine, and low-dose neuroleptics may suppress choreoathetotic movements but are often ineffective.

TICS Stereotypical,purposeless movements such as eye blinks, sniffling,

and clearing of the throat. Gilles de la Tourette syndrome is a rare but severe

multiple tic disorder that may involve motor tics (especially twitches of the face, neck,and shoulders),vocal tics (grunts, words), and “behavioral tics”

(coprolalia,echolalia). The cause is unknown. Haloperidol usually reduces