TABLE 10-3-ISOLATED MOTOR SYSTEMS INVOLVEMENT: GENERAL CHARACTERISTICS ON EXAMINATION

COMPONENTS OF THE MOTOR EXAMINATION: 1. Observation. 2. Palpation and percussion. 3. Passive resistance. 4. Strength. 5. Coordination: a. rapid repeating alternating movement; b. finger to nose, etc. 6. Gait. 7. Deep-tendon reflexes.

MUSCLE: MYOSITIS AND DYSTROPHY

Examination

  1. Proximal wasting prominent.
  2. Myositic muscle may be tender to palpation.
  3. Decreased resistance.
  4. Proximal weakness predominant with late distal involvement.
  5. Coordination
    1. Slow and irregularly clumsy.
    2. Slow, but accurate if strong enough.
  6. Difficulty climbing and descending stairs, running, rising from chair or floor, or crossing obstacles; waddling gait.
  7. Tendon reflexes usually present, but depressed in parallel to weakness.

Special Studies

  1. EMG and NCV: Decreased units diffusely with small, fast, myopathic potentials; normal conduction time.
  2. Normal edrophonium or neostigmine test (e.d., no increased strength).
  3. No fasciculations with neostigmine.
  4. Biopsy: diffuse muscle degeneration, inflammatory infiltrate in myositis, noninflammatory degeneration if dystrophy.
  5. Elevated level of serum muscle enzymes (creatine phosphokinase most sensitive); may not be elevated in late or chronic myositis and dystrophy. A useful measurement in evaluating course of disease and results of therapy.
  6. Thyroid deficiency or excess may be present.

NEUROMUSCULAR JUNCTION: MYASTHENIA GRAVIS

Examination

  1. Extraocular muscle system most frequently involved early. Other bulbar muscles frequently involved, distal and proximal muscles of extremities affected less and later as a rule. Atrophic changes occur from disuse; dystrophic features in long-standing disease, possibly related in part to chronic anticholinesterase effect.
  2. Nontender.
  3. Decreasing tone with increasing weakness.
  4. Characteristic increasing weakness with exercise with unusually prompt recovery to almost normal strength on resting early; increasingly irreversible weakness with progression of disease.
  5. Slow but usually accurate.
  6. As with diffuse weakness, but frequently not severely involved because extremity muscles are less affected.
  7. Progressive decrease in DTR response with repeated tendon tapping.

Special Tests

  1. EMG and NCV: Progressively decreasing muscle potentials with exercise or repeated motor nerve stimulation.
  2. Neostigmine and edrophonium cause prompt strengthening and resistance to fatigue in affected muscles (less reliable with extraocular myasthenia).
  3. Biopsy nonspecific.

Special Study

Neuromuscular postsynaptic membrane antibodies detectable in serum.

PERIPHERAL NERVE: NEUROPATHY

Examination

  1. Distal atrophy prominent, occasional fasciculations.
  2. Sensory abnormalities usually associated, and therefore patients have concomitant sensory symptoms (hypoesthesia, paresthesia, etc.)
  3. Decreased tone.
  4. Distal weakness predominates.
  5. Where proprioception is lost, closure of eyes results in misplacements (if in lower extremities, positive Romberg sign).
  6. As with distal weakness and proprioceptive loss.
  7. Depressed to absent DTRs.

Special Studies.

  1. Decreased conduction time with demyelinating neuropathies, occasional fasciculations and giant summation potentials on EMG.
  2. Neostigmine may bring out fasciculations.
  3. Biopsy reveals motor unit dropout and neuronal damage.
  4. Evidence of malnutrition (folic acid level decreased), diabetes mellitus, thyroid deficiency, vitamin B.2 deficiency, uremia, porphyria, heavy metal poisoning to be sought among others by appropriate blood, urine and stool studies.

VENTRAL ROOT: ACUTE AND SUBACUTE POLYNEUROPATHY

Examination

  1. Nonspecific, occasional fasciculations.
  2. Nonspecific, nontender.
  3. Decreased tone.
  4. Ascending weakness frequent (Landry, Guillain Barre, and carcinomatous radiculopathy) with distal prominence through occasional major proximal prominence early.
  5. Slow, but accurate if able.
  6. Nonspecific.
  7. Usually absent DTRs.

Special Tests

  1. Nerve conduction slowed; EMG with occasional fasciculations and decreased mass response (interference pattern).
  2. Neostigmine may increase fasciculations.
  3. Level of protein in cerebrospinal fluid up; cells normal (if cells are increased or not, cytologic tests should be done for malignant cells).

ANTERIOR HORN CELL: POLIOMYELITIS, AMYOTROPHIC LATERAL SCLEROSIS

Examination

  1. Patchy atrophy from single muscles to large masses; fasciculations not prominent. (In amyotrophic lateral sclerosis, there tends to be symmetric involvement with prominent fasciculations.)
  2. Tender early in polio.
  3. Decreased tone, unless contractures. (in ALS, tone may be increased, decreased, or normal depending on balance of anterior horn/long-tract involvement)
  4. Weakness appropriate to distribution and severity of atrophy.
  5. Nonspecific.
  6. Depends on muscle groups involved.
  7. Depressed to absent DTRs in proportion to weakness. (in ALS, increased, decreased, or normal depending on balance of anterior horn/long tract involvement)

Special Studies

  1. EMG: fasciculations, fibrillations, and giant summation potentials in involved muscles.
  2. Neostigmine may cause marked increase in fasciculations.
  3. Throat, stool virus cultures for polio suspect. Most recent cases of polio are related to live virus vaccine complications.

PYRAMIDAL SYSTEM: PRIMARY LATERAL SCLEROSIS*

Examination

  1. Minimal atrophy; prominent flexor hypertonus; flexor spasms occur with severe involvement.
  2. Nonspecific.
  3. Clasp-knife rigidity.
  4. Distal muscles tend to be predominantly involved with unilateral involvement.
  5. Slow, irregularly clumsy.
  6. Spastic-scissors and stiff leg gait; decreased arm swing.
  7. DTRs hyperactive with clonus; abdominals depressed; Babinski response present

Special Studies

  1. To determine site of lesion, neuroradiologic studies such as myelogram, angiography, CT scan, MRI may be needed to supplement more routine tests (i.e., lumbar puncture, EEG, skull and spine x-rays) when diagnosis is not secure.

CEREBELLUM

Examination

  1. Intention tremor (rhythmic oscillatory tremor three to eight per second, absent at rest) on side of lesion.
  2. Nonspecific.
  3. Decreased tone.
  4. May see mild weakness of diffuse nature in involved extremities.
  5. Past and under pointing, severe dyscoordination on RRAM.
  6. Wide-based ataxic (drunk) gait with falling to side of lesion; may see narrow or normally based gait with severe retropulsion when lesion is in midline vermis region.
  7. DTRs usually normal but may be pendular.

Special Tests

  1. CT scan, MRI, angiography of vertebrobasilar system, lumbar puncture.

BASAL GANGLIA: PARKINSONISM

Examination

  1. Hyper and hypokinesia
    1. Three to eight per second tremor, present with tonic posturing and at rest. (Muscle must, however, have resting tonus to see tremor.)
    2. Bradykinesia (e.g., difficulty initiating movement, masked facies).
  2. Nonspecific.
  3. Cogwheel-plastic rigidity.
  4. May have some weakness of disuse.
  5. Bradykinesia; may be quite coordinated after movement is initiated.
  6. Flexed trunk, small steps; retropulsion if pushed backward or walks backward.
  7. Normal reflexes, occasionally depressed.

BASAL GANGLIA: HUNTINGTON'S CHOREA

Examination

  1. Irregular, jerky, involuntary movements associated with progressive dementia; autosomal dominant so family history is the rule.

Special Test

  1. CT scan and MRI reveal caudate nucleus atrophy.

BASAL GANGLIA: HEMIBALLISM

Examination

  1. Gross flailing to mild choreic movements (contralateral to subthalamic nucleus lesion) make diagnosis obvious. Patient may die of exhaustion; however, movements are normally self-limited if caused, as is frequently the cause, by ischemia-infarction.

BASAL GANGLIA: ATHETOSIS

Examination

  1. Slow, writhing movements, particularly involving proximal muscles and trunk, associated with 'progressive dementia. (Huntington's chorea frequently has athetoid components.)

RETICULAR FORMATION

Examination

  1. Lesions characterized by decerebrate or decorticate rigidity if between low pons and low diencephalon (see text).

*A form of motor neuron disease presumed to be part of the spectrum of amyotrophic lateral sclerosis with little detectible anterior horn cell involvement.

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