Asynergy refers to impaired coordination of muscles or organs that normally function in a harmonious and integrated manner. It manifests as uncoordinated movements, inaccurate timing of muscle contractions, or disruption of the smooth execution of motor tasks. Asynergy is commonly an extrapyramidal symptom resulting from disorders affecting the basal ganglia and cerebellum.

Pathophysiology

Normal motor coordination depends on precise integration of signals between the cerebral cortex, basal ganglia, cerebellum, brainstem, and spinal cord. The basal ganglia regulate the initiation and amplitude of movements, while the cerebellum fine-tunes timing, force, and sequencing. Lesions or dysfunction in these areas disrupt this integration, leading to asynergy. Causes include stroke, cerebellar degeneration, Parkinson’s disease, multiple sclerosis, or toxic/metabolic insults affecting motor pathways.

Examination Technique

• Observation: Watch for abnormal posture, tremor, or unsteady gait.

• Finger-to-nose test: Ask the patient to alternately touch their nose and your finger; incoordination indicates cerebellar involvement.

• Heel-to-shin test: Have the patient slide their heel down the opposite shin; irregular or inaccurate movement suggests lower limb asynergy.

• Rapid alternating movements: Evaluate pronation-supination of the hands; dysrhythmic or slowed movements indicate extrapyramidal involvement.

• Functional assessment: Assess for impaired coordination during routine activities (e.g., dressing, eating).

Clinical utility

• Diagnostic clue: Helps localize neurologic lesions to the cerebellum or basal ganglia.

• Monitoring disease progression: Repeated assessments can track deterioration or improvement.

• Guiding therapy: Identifies specific deficits that may benefit from physiotherapy or pharmacologic management.

Differential Diagnosis

History and Physical Examination

• History: Ask about onset, progression, associated tremor or weakness, history of stroke, neurodegenerative disease, toxin exposure, or medications.

• Examination: Evaluate gait, posture, muscle tone, strength, reflexes, and presence of tremor or dysarthria. Document limb and trunk coordination deficits.

Diagnostic approach

• Neuroimaging: MRI or CT to detect structural lesions in the cerebellum, basal ganglia, or brainstem.

• Electrophysiologic studies: EMG and nerve conduction studies may help differentiate central vs. peripheral causes.

• Laboratory tests: Evaluate metabolic causes (thyroid, liver, electrolyte abnormalities) or toxin exposure.

• Functional assessments: Standardized scales such as the International Cooperative Ataxia Rating Scale (ICARS) or Unified Parkinson’s Disease Rating Scale (UPDRS).

Management

• Address underlying disorder: Stroke rehabilitation, Parkinson’s medications (e.g., levodopa), immunomodulation in MS, or withdrawal of offending drugs.

• Physical therapy: Exercises to improve balance, coordination, and fine motor skills.

• Occupational therapy: Adaptation for daily activities and assistive devices.

• Symptomatic treatment: Tremor control with medications if indicated; botulinum toxin for focal dystonia.

Patient counseling

• Explain the neurological basis of incoordination and potential for improvement with therapy.

• Encourage adherence to physiotherapy and home exercises to maintain function.

• Discuss prognosis, which depends on underlying cause and extent of neurologic damage.

Pediatric considerations

• Pediatric asynergy may result from congenital cerebellar malformations, perinatal hypoxia, or inherited ataxias.

• Early intervention with therapy is critical for motor development.

Geriatric considerations

• Age-related neurodegeneration and polypharmacy can exacerbate asynergy.

• Fall prevention and environmental modifications are important to reduce injury risk.

Key points

• Asynergy is a sign of impaired coordination due to cerebellar or basal ganglia dysfunction.

• It provides important localization information in neurologic assessment.

• Management focuses on underlying disease, rehabilitation, and symptom control.

References

1. Buttaro TM, Tybulski J, Bailey PP, Sandberg-Cook J. Primary Care: A Collaborative Practice. St. Louis, MO: Mosby Elsevier; 2008. p. 444–447.

2. McCance KL, Huether SE, Brashers VL, Rote NS. Pathophysiology: The Biologic Basis for Disease in Adults and Children. 8th ed. Maryland Heights, MO: Mosby Elsevier; 2019.

3. Klockgether T. Ataxia. N Engl J Med. 2010;362:1907–1919.

4. Jankovic J. Parkinson’s Disease: Clinical Features and Diagnosis. J Neurol Neurosurg Psychiatry. 2008;79:368–376.

5. Tintinalli JE, Stapczynski JS, Ma OJ, Yealy DM, Meckler GD, Cline DM. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 9th ed. New York, NY: McGraw-Hill; 2020.