14.1 Parkinson Disease and Basal Ganglia Disorders
Key Takeaways
Nigrostriatal dopamine loss reduces direct-pathway facilitation and removes restraint on the indirect pathway in the classic circuit model, increasing inhibitory output to the thalamus.
The MDS definition of motor parkinsonism requires bradykinesia plus rest tremor or rigidity. Postural instability affects function and requires assessment, even though it is not part of that motor definition.
Hoehn and Yahr Stage 3 adds postural instability to bilateral disease while physical independence is retained in the scale’s staging sense. Assess specific tasks and support needs separately.
Use standardized mobility and balance tests to document performance. Interpret repeat scores with medication timing, aid use, falls history and observed function.
Individualize external cues, task-specific practice, progressive strength and balance training and aerobic exercise. The original LSVT BIG protocol uses 16 one-hour sessions over four weeks.
Parkinson Disease and Basal Ganglia Disorders
Neuropathology and Basal Ganglia Circuitry
Parkinson disease involves degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc) and reduced dopamine in the striatum. Lewy bodies containing alpha-synuclein are characteristic of typical Parkinson pathology. Clinical assessment is based on the motor syndrome and other diagnostic features, and the disease also affects nonmotor systems.
The classic direct/indirect pathway model explains one effect of dopamine loss on movement. The internal globus pallidus (GPi) and substantia nigra pars reticulata (SNr) send inhibitory output to motor targets including the thalamus. The motor thalamus normally excites cortical motor areas.
- Direct pathway. Activation of striatal neurons reduces GPi/SNr output. This releases some of the thalamus from inhibition and facilitates motor activity. Dopamine acts at D1 receptors to facilitate this pathway.
- Indirect pathway. Striatal inhibition of the external globus pallidus (GPe) releases the subthalamic nucleus (STN) from part of the GPe's inhibition. The STN excites GPi/SNr, which increases inhibition of the thalamus. Dopamine acts at D2 receptors to restrain activity in this pathway.
With dopamine loss, less direct-pathway inhibition of GPi/SNr and greater indirect-pathway drive both favor increased inhibitory output. This helps explain difficulty initiating and scaling movement. Real circuits also have parallel routes and abnormal activity patterns. The simple model cannot explain every symptom or predict an individual's response to exercise.
Motor Examination
The MDS clinical criteria define motor parkinsonism by bradykinesia plus rest tremor or rigidity. Other clinical findings are then used in determining whether Parkinson disease explains the syndrome. TRAP is a memory aid for four common motor findings in Parkinson disease.
| Finding | Recognition and practical implication |
|---|---|
| Tremor | A characteristic rest tremor is often 4–6 Hz and may diminish with voluntary action. Observe the limbs at rest as well as in posture and movement. Some patients have no rest tremor. |
| Rigidity | Resistance can be evident during slow passive movement in either direction. Smooth resistance is called lead-pipe rigidity, and ratcheting can be felt as cogwheeling. Compare this pattern with a velocity-dependent catch in spasticity. Consider pain, guarding and joint restriction as other contributors to passive resistance. |
| Akinesia, bradykinesia and hypokinesia | Akinesia describes an absence or difficulty initiating movement. Bradykinesia includes slowness with decrement in speed or amplitude or progressive hesitations or arrests on repetition. Hypokinesia describes reduced movement amplitude. Observe a repetitive task such as finger tapping and note the pattern across repetitions, not just the speed of the first movement. |
| Postural instability | Reduced ability to recover after a perturbation can affect turning, reaching and responses to trips. Assess reactive stepping with appropriate guarding. Compare it with voluntary stepping and the person's history. |
During the standardized MDS-UPDRS motor examination, the pull test assesses reactive stepping after a controlled backward perturbation. The examiner prepares to catch the patient and records the steps and whether recovery was independent. Needing a catch is more impaired than taking several steps and recovering without help. Follow the instrument instructions and document the assistance, especially if the test cannot be performed safely. A pull test result is distinct from the broader Hoehn and Yahr stage.
Gait and Nonmotor Features
Festination can appear as increasingly rapid, short steps. Freezing of gait is a brief episode of absent or markedly reduced progression despite the intention to walk. Ask about starting, turning, narrow passages and multitasking. Freezing may be absent during straight walking in the clinic. Assess a relevant trigger with guarding and document how the patient resumes walking. Reduced arm swing, facial expression, handwriting size or voice volume can also occur.
Ask about nonmotor symptoms affecting the rehabilitation plan, including orthostatic lightheadedness, constipation or urinary symptoms, sleep, mood, cognition and fatigue. Dysphagia or a change in speech may warrant appropriate referral. Parkinson disease can contribute to autonomic dysfunction, and medication effects or other conditions can contribute as well. When indicated, check orthostatic blood pressure using a standardized supine-to-standing procedure, record the symptoms and coordinate evaluation with the medical team.
Staging and Functional Outcome Measures
The original Hoehn and Yahr scale describes overall motor stage. Modified versions add intermediate stages. Name the version in documentation and interpret the stage with a separate assessment of tasks and support needs.
| Stage | Broad clinical description |
|---|---|
| 1 | Unilateral involvement. |
| 1.5, modified | Unilateral involvement with axial findings. |
| 2 | Bilateral or midline involvement without balance impairment in the original scale. The modified scale specifies bilateral involvement. |
| 2.5, modified | Mild bilateral involvement with recovery on the pull test. |
| 3 | Mild to moderate bilateral disease with some postural instability. The person remains physically independent in the staging description. |
| 4 | Severe disability, with the ability to stand or walk without physical help still present. |
| 5 | Uses a wheelchair or remains in bed unless assisted. |
A stage does not certify independence at home. For example, someone with Stage 3 may walk without physical assistance on a straight, open route and still need supervision on stairs or during freezing episodes.
The MDS-UPDRS has four parts. Part I covers nonmotor experiences of daily living, Part II covers motor experiences of daily living, Part III is the motor examination, and Part IV covers motor complications. For reassessment, record medication timing and whether the patient is in an ON or OFF state when applicable. Pair broad ratings with a measure that addresses the treatment objective.
| Measure | Clinical use |
|---|---|
| TUG | Times a sequence of transfers, walking and turning. Note assistance, the usual aid, the number of turning steps and any freezing. |
| Berg Balance Scale | Samples functional balance tasks, scored out of 56. Inspect difficult items and possible ceiling effects. |
| Mini-BESTest | Samples anticipatory and reactive balance, sensory orientation and dynamic gait. The standard 14 items are scored 0–2 for a total out of 28. Use the standard scoring instructions when bilateral items are tested. |
| Gait speed or freezing history | A standardized walk can show a change in speed. A record of freezing episodes or a freezing questionnaire can capture problems in environments the timed trial does not sample. |
Use the scores to describe performance and target training. Fixed score bands cannot establish whether a person will fall or can live independently. Record recent falls, environmental triggers and the assistance required for daily tasks.
Physical Therapy Interventions
1. External Cueing and Gait Practice
Choose a cue based on the movement problem and the patient's response. Visual floor targets can provide a spatial reference for step length. A metronome or rhythmic sound can give timing for stepping. Try a rhythm near the patient's comfortable cadence and adjust if it causes rushing, smaller steps or instability. A spoken cue such as “take a long step” can direct attention to movement amplitude. Evidence supports cueing for gait and freezing outcomes, with response varying by person and task.
For doorway freezing, practise pausing, stabilizing, shifting weight and taking a deliberate step to a visible target if this works for the patient. Use a safe route and close guarding when needed. Turn through a wider arc or with deliberate steps instead of forcing a rapid pivot when that provokes freezing. Establish whether the cue transfers to the home and fits the patient's attention, vision and hearing.
2. Amplitude-Based Practice
LSVT BIG is a structured amplitude programme. The original studied format used 16 one-hour individual sessions over four weeks, with four supervised sessions per week and assigned home practice. Rehearse large controlled movements and meaningful tasks such as rising from a chair, reaching or stepping through a doorway. Progress toward use during everyday tasks. The aim is to improve movement amplitude and function. Adjust the plan to the patient's symptoms and capacity.
3. Balance, Task-Specific and Multicomponent Exercise
Train voluntary and reactive stepping, transfers, changes of direction and obstacles within a setup that permits appropriate guarding. Progress a single task before adding a distracting motor or cognitive task when it is safe and relevant. For example, practise turning without freezing first, then assess whether carrying a light item affects the turn. Teach the patient to pause a secondary task when safe walking demands more attention.
The APTA guideline supports moderate- to high-intensity aerobic exercise where appropriate, progressive resistance training, balance training, gait training and task-specific practice for idiopathic Parkinson disease. Choose the mode and dose according to baseline function, safety and symptom response. Stationary cycling can be useful when walking requires close supervision. Check exertional response and consider perceived exertion when autonomic dysfunction or medication alters the heart-rate response. Exercise can improve fitness, motor symptoms and function. A functional gain alone cannot establish a disease-modifying effect.
Worked Case: Doorway Freezing and Falls
A 69-year-old with Stage 3 Parkinson disease reports two falls in the last month. He freezes at his kitchen doorway and while turning. In the clinic he walks with a cane, needs a catch on the reactive pull test and completes a TUG in 21.0 seconds. His Mini-BESTest score is 16/28. He takes small steps on the turn and stalls at the doorway. Identify which tasks provoke freezing and whether lightheadedness, medication fluctuations or hazards also contribute. Plan guarded turning and stepping practice, trial a visible doorway cue with spacing chosen from a safe step length, and add progressive balance, strength and conditioning. Agree on a way to record falls and freezing episodes at home.
Four weeks later, the TUG takes 13.2 seconds with the same cane and comparable medication timing, 7.8 seconds faster. The Mini-BESTest is 22/28, a 6-point gain. He reports better doorway initiation with the cue but still freezes when carrying a cup and turning. The scores and observed task performance support progression of the successful strategies. Review home performance, fall history and the need for supervision separately.
In the classic basal ganglia model, what effect of nigrostriatal dopamine loss helps explain bradykinesia in Parkinson disease?
Less direct-pathway facilitation and greater indirect-pathway activity increase inhibitory output from GPi/SNr to the thalamus.
Less dopamine increases direct-pathway inhibition of GPi/SNr, increasing thalamic inhibition.
The indirect pathway becomes less active and the subthalamic nucleus sends less excitatory input to GPi/SNr.
Nigral dopamine loss directly increases excitatory output from GPi/SNr to the thalamus.
A patient with bradykinesia has smooth resistance throughout slow passive elbow flexion and extension, without a velocity-dependent catch. The resistance is not explained by pain or a joint block. Which motor finding best fits this examination?
Clasp-knife spasticity.
Lead-pipe rigidity.
Clonus.
Cogwheel rigidity with distinct ratcheting.
A patient with bilateral Parkinson motor signs develops postural instability but remains physically independent. Which stage of the original Hoehn and Yahr scale best describes this presentation?
Stage 1.
Stage 2.
Stage 3.
Stage 5.
A patient freezes at a doorway and takes progressively shorter steps when a fast metronome is used. Which supervised adjustment best addresses the problem?
Increase the metronome rate further to make the patient step faster.
Ask the patient to add a verbal fluency task during every doorway trial.
Use a fixed cue rate for every patient with freezing.
Try a visible stepping target at a safe step length and observe whether initiation and stability improve.
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