The motor system can fail in two distinct ways that produce two very different patterns of abnormal tone. The pyramidal (corticospinal) system produces spasticity — velocity-dependent resistance that gives way suddenly. The extrapyramidal (basal ganglia and related circuits) system produces rigidity — velocity-independent resistance that is constant throughout the range. Both produce a stiff limb; the patterns of stiffness are different in ways that the bedside exam can distinguish in about thirty seconds. Recognizing the pattern points to entirely different families of disease.

This page covers the bedside distinction between pyramidal and extrapyramidal motor system disease, the patterns of each, and the syndromes that produce them. The skill being developed is the ability to lift a patient’s arm or move a leg passively and to recognize what kind of stiffness you are feeling.

The Two Motor Systems

The Pyramidal System

The pyramidal system (corticospinal tract) carries voluntary motor commands from the cortex to the spinal cord. Cell bodies of origin are in the primary motor cortex (precentral gyrus) and adjacent premotor and supplementary motor areas. Axons descend through the corona radiata, the posterior limb of the internal capsule, the cerebral peduncle of the midbrain, the basis pontis, and the medullary pyramid, where the vast majority (about 85%) decussate at the pyramidal decussation before continuing in the lateral corticospinal tract of the cord. The remaining fibers descend uncrossed in the anterior corticospinal tract and decussate at the segmental level. Most fibers synapse on spinal interneurons; only a minority (about 15-20%) synapse directly on alpha motor neurons.

The functional output of the pyramidal system is fine, distal, fractionated movement — the dexterity of the hand. A pyramidal lesion produces weakness predominantly affecting these fine movements, with relative preservation of more proximal and gross movements. The pattern of weakness is characteristically distal > proximal, with the upper extremity extensors weaker than flexors, and lower extremity flexors weaker than extensors. This pattern explains the classical posture of hemiplegic stroke: arm flexed at elbow and wrist, leg extended at hip and knee.

The Extrapyramidal System

The extrapyramidal system encompasses the basal ganglia (caudate, putamen, globus pallidus, subthalamic nucleus, substantia nigra) and their cortical and brainstem connections. Output reaches the spinal cord indirectly, through the reticulospinal, rubrospinal, vestibulospinal, and tectospinal tracts. The system functions to modulate motor activity — selecting desired movements, suppressing unwanted ones, setting muscle tone and posture, and contributing to the automatic components of movement.

An extrapyramidal lesion does not produce weakness in the way a pyramidal lesion does. Instead it produces abnormalities of tone (rigidity), abnormalities of speed (bradykinesia or hyperkinetic movements), abnormalities of posture (stooped, with loss of postural reflexes), and abnormalities of the automatic accompaniments of movement (reduced arm swing, masked facies, hypophonic speech).

Pyramidal Findings (Upper Motor Neuron Signs)

A lesion of the corticospinal tract anywhere from cortex to cord produces a recognizable cluster of findings:

• Weakness: distal > proximal, with pyramidal pattern (upper extremity extensors weaker, lower extremity flexors weaker).
• Spasticity: velocity-dependent increased tone. The faster you move the limb, the greater the resistance. Often described as a “clasp-knife” — the resistance builds, then suddenly gives way.
• Hyperreflexia: brisk deep tendon reflexes, sometimes with reflex spread to adjacent muscle groups and sometimes with clonus.
• Clonus: rhythmic involuntary contractions in response to sustained stretch. Most often seen at the ankle (jerking the foot up sharply produces sustained beats).
• Babinski sign and other extensor toe responses: the great toe extends in response to plantar stimulation. Discussed in detail on the Babinski Sign page.
• Loss of superficial reflexes: abdominal reflexes, cremasteric reflex.
• Pronator drift: with arms outstretched and palms up, the affected arm drifts downward and the forearm rotates into pronation. A sensitive early sign.

Spasticity

Spasticity is the cardinal pyramidal sign and the one most useful for distinguishing pyramidal from extrapyramidal disease. It is velocity-dependent — moving the limb slowly produces little or no resistance; moving it quickly produces sudden, marked resistance that may give way at the end of the range. The “clasp-knife” character — resistance throughout the early range, then sudden release — is classic and distinct from any extrapyramidal pattern.

To test for spasticity, support the patient’s elbow with one hand and the wrist with the other. Move the elbow slowly through flexion and extension, then more quickly. Repeat at the wrist, the knee, and the ankle. Spasticity will be most evident at the elbow and the ankle, with extension at the elbow and dorsiflexion at the ankle producing the strongest resistance. The “Achilles” muscle test — quick dorsiflexion of the ankle, often producing several beats of clonus — is the most reliable bedside spasticity assessment.

Spasticity vs Spasms

Spasticity (tone change) is distinct from spasm (an involuntary sustained contraction). A patient with severe spasticity may have spontaneous flexor or extensor spasms — particularly in chronic spinal cord disease — but these are different findings. Spasms are episodic and obvious; spasticity is detected on passive movement of the relaxed limb.

Extrapyramidal Findings

The extrapyramidal cluster is fundamentally different from the pyramidal one:

• Rigidity: velocity-independent increased tone. The resistance is constant throughout the range of movement, present whether the limb is moved slowly or quickly. Two subtypes:
  • Lead-pipe rigidity: smooth, sustained resistance. Often seen in advanced parkinsonism.
  • Cogwheel rigidity: the smooth resistance is interrupted by a regular catching, as if rolling over the teeth of a cog. Reflects superimposition of a 4-6 Hz tremor on background rigidity. Best appreciated at the wrist.
• Bradykinesia: slowness and poverty of movement. The hallmark of parkinsonism. Detected on the patient’s spontaneous movements (slow rising from the chair, slow walking, reduced facial expression, reduced arm swing) and on rapid alternating movements (finger taps, hand grips, foot taps) which show progressive reduction in amplitude with continued effort.
• Tremor: characteristically present at rest in Parkinson disease. The classical “pill-rolling” 4-6 Hz tremor of the hand, often unilateral at onset, reducing or disappearing with voluntary movement. Other extrapyramidal tremors exist (essential tremor, dystonic tremor) and are discussed on the Abnormal Movements page.
• Postural instability: loss of the postural reflexes that maintain balance during disturbance. Tested by the pull test — standing behind the patient and giving a firm tug backward at the shoulders. The normal response is a few small backward steps with rapid recovery. The parkinsonian patient takes several uncontrolled steps backward (retropulsion) and may fall.
• Reduced arm swing during gait, often asymmetric — the arm on the more affected side swings less. Often the first sign of unilateral parkinsonism.
• Masked facies (hypomimia): reduced spontaneous facial expression, blink rate (normal 15-20/min, parkinsonian patients about 5-7/min), and emotional reactivity of the face.
• Hypophonic, monotonous speech: reduced volume, prosody, and articulation. Often described by the patient’s family as “mumbling” or “talking softly.”
• Stooped posture: flexed at the trunk, hips, and knees. The “Statue of Liberty” posture in advanced disease, with all major joints in mild flexion.
• Glabellar tap (Myerson sign): tapping the glabella produces blinks that normally habituate after a few taps. In parkinsonism, blinking continues throughout.

The Pull Test (Postural Reflexes)

The pull test is one of the most informative bedside exams for parkinsonism and one of the most consistently underused. Stand behind the patient, place your hands on their shoulders, warn them that you are going to pull them backward, and give a firm, deliberate pull at the shoulders. Be prepared to catch them. The normal response is one or two small backward steps with prompt recovery; the parkinsonian response is several uncontrolled backward steps (retropulsion) or a fall. The pull test deteriorates progressively in advanced parkinsonism and is the most reliable predictor of falls.

Distinguishing Pyramidal from Extrapyramidal Disease

The two systems can fail together. Multiple system atrophy combines parkinsonism with corticospinal signs. Vascular disease can produce a combination. ALS combines lower motor neuron disease with upper motor neuron signs. The combinations are diagnostically informative — pure pyramidal disease points to cord, capsule, or motor cortex; pure extrapyramidal disease points to basal ganglia; combinations point to disorders that involve both systems.

Common Syndromes

Pyramidal Disease Syndromes

• Hemiplegic stroke: acute onset, contralateral hemiparesis with classical pyramidal pattern. Cortical or subcortical (capsular). Often with cortical signs (aphasia if dominant, neglect if non-dominant) when cortical.
• Spastic paraparesis: chronic bilateral lower extremity spasticity. Causes include hereditary spastic paraplegia (HSP), MS, cervical or thoracic myelopathy, primary lateral sclerosis, tropical spastic paraparesis (HTLV-1), B12 deficiency (with dorsal column features).
• Brown-Séquard syndrome: hemisection of the cord; ipsilateral pyramidal weakness with contralateral pain/temperature loss.
• Cerebral palsy: childhood-onset pyramidal signs (and often other features) from perinatal brain injury.

Extrapyramidal Disease Syndromes

• Idiopathic Parkinson disease: progressive degeneration of the substantia nigra pars compacta. The classical tetrad of bradykinesia, rest tremor, rigidity, and postural instability. Asymmetric onset is typical. Response to levodopa is the diagnostic feature in addition to the clinical picture.
• Progressive supranuclear palsy (PSP): parkinsonism with prominent vertical gaze palsy (especially downgaze), early postural instability with backward falls, axial rigidity, and frontal cognitive dysfunction. Poor response to levodopa.
• Multiple system atrophy (MSA): parkinsonism with autonomic failure (orthostatic hypotension, urinary dysfunction), cerebellar features (MSA-C), or both. Poor response to levodopa.
• Corticobasal syndrome: asymmetric parkinsonism with apraxia, alien limb, dystonia, and cortical sensory loss.
• Dementia with Lewy bodies: parkinsonism with prominent cognitive fluctuations, visual hallucinations, and dementia early in the course.
• Vascular parkinsonism: bilateral parkinsonism with lower-body predominance (“lower-half parkinsonism”), often with gait apraxia and minimal tremor; reflects multiple subcortical infarcts.
• Drug-induced parkinsonism: from dopamine receptor antagonists (haloperidol, risperidone, metoclopramide, prochlorperazine). Symmetric onset, often with reduced response to levodopa, reversible on discontinuation (though sometimes slowly).

Hyperkinetic Extrapyramidal Disorders

The other extrapyramidal pattern is excess movement rather than reduced movement. Chorea, athetosis, ballism, dystonia, tics, and myoclonus are all extrapyramidal hyperkinetic movements; they are covered in detail on the Abnormal Movements page. The point here is that not all extrapyramidal disease is parkinsonism — the system controls movement in both directions, and the hyperkinetic disorders are the opposite face of basal ganglia dysfunction.

🔍 Did You Know?

The classical glabellar tap (Myerson sign) — tapping the glabella and watching for failure to habituate — is reasonably sensitive for parkinsonism but is not specific. It is also seen in frontal lobe disease, in advanced Alzheimer disease, in normal pressure hydrocephalus, and as a normal variant in some elderly patients. Its diagnostic value is in the context of other parkinsonian features, not in isolation. The presence of cogwheel rigidity in a patient with a positive glabellar tap and a unilateral reduction in arm swing is, however, almost diagnostic of parkinsonism.

Pitfalls and Pearls

• Spasticity is velocity-dependent; rigidity is not. Move the limb slowly and quickly; the difference declares the pattern.
• Cogwheel rigidity reflects superimposed tremor on background rigidity. It is best appreciated at the wrist with the elbow at 90 degrees, the examiner’s hand controlling the patient’s hand.
• Pronator drift is the earliest UMN sign. Test it on every patient with possible hemispheric or brainstem disease.
• The pull test is underused. A patient who falls on the pull test has substantially elevated fall risk and may warrant intervention (mobility aids, fall prevention strategies, levodopa adjustment).
• Asymmetric onset of parkinsonism favors idiopathic PD. Symmetric onset, vertical gaze palsy, early postural instability, autonomic failure, or rapid progression should raise concern for atypical parkinsonism.
• Drug-induced parkinsonism is a common cause of new parkinsonism. Ask about all dopamine-blocking medications, including antiemetics (metoclopramide) and the older antipsychotics. Often reversible.
• Hemiparkinsonism (entirely one-sided) can be the presenting picture of corticobasal syndrome, of striatal lesion, or rarely of idiopathic PD.
• Lower-half parkinsonism (gait abnormalities greater than arm involvement) points to vascular parkinsonism, normal pressure hydrocephalus, or atypical PD.
• A patient with frontal release signs, pseudobulbar affect, and gait apraxia has bilateral frontal disease — vascular dementia, frontotemporal dementia, or normal pressure hydrocephalus, not parkinsonism.
• Both systems can fail together. ALS, multiple system atrophy, certain leukodystrophies, and B12 deficiency produce mixed pictures.

References

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