Huntington Disease

Populations and Risk Factors

Autosomal dominant inheritance — 50% chance of transmission from an affected parent; all carriers who inherit the expanded allele (>40 CAG repeats) will develop the disease
Typical onset between ages 35–50; juvenile HD (onset before age 20) accounts for ~5–10% of cases and presents with a distinct clinical picture (rigidity predominant, seizures, rapid decline)
Affects all racial groups and both sexes equally; prevalence is approximately 5–10 per 100,000 in populations of European descent
Anticipation phenomenon: The CAG repeat tends to expand in successive generations, particularly through paternal transmission — offspring may develop the disease earlier and more severely than the affected parent; a key genetic counseling concept
CAG repeat length correlates with onset: 36–39 repeats = reduced penetrance (may or may not develop symptoms); 40+ repeats = full penetrance; 60+ repeats = juvenile onset
No environmental risk factors modify onset or progression once the gene is inherited — HD is entirely genetically determined
Significant psychological burden: presymptomatic genetic testing reveals whether a person will develop a fatal, untreatable disease, creating profound ethical and emotional implications

Causes and Pathophysiology

The Genetic Mutation

The HTT gene on chromosome 4p16.3 normally contains 10–35 CAG trinucleotide repeats coding for the amino acid glutamine. In HD, the repeat expands beyond 36 copies, producing an abnormally long polyglutamine tract in the huntingtin protein.
The mutant huntingtin protein misfolds, forms intranuclear aggregates, and becomes toxic to neurons. The precise mechanism of toxicity involves disrupted gene transcription, impaired mitochondrial function, excitotoxicity from excess glutamate, and impaired intracellular protein transport.

Basal Ganglia Degeneration

The caudate nucleus and putamen (collectively the striatum) are the earliest and most severely affected structures. These nuclei are critical components of the basal ganglia motor circuit, which modulates voluntary movement by balancing excitatory and inhibitory signals to the thalamus and cortex.
GABAergic medium spiny neurons in the striatum are selectively destroyed. These neurons normally inhibit the globus pallidus externa and substantia nigra pars reticulata. Loss of this inhibitory output results in excessive thalamic excitation of the motor cortex — producing the involuntary, purposeless movements (chorea) that define the early disease.
As degeneration progresses, the basal ganglia lose the ability to coordinate any movement — the early hyperkinetic phase (chorea) transitions to a late hypokinetic phase (rigidity, bradykinesia, akinesia), similar in appearance to advanced Parkinson disease but with a fundamentally different mechanism.
Dying neurons are replaced by astrocytes (gliosis), which cannot perform the specialized neurotransmitter functions of the lost neurons. The caudate nucleus visibly atrophies on imaging, and the lateral ventricles enlarge (hydrocephalus ex vacuo).

Neurotransmitter Disruption

Decreased GABA and acetylcholine in the striatum removes inhibitory control over the thalamus, resulting in over-release of glutamate to the frontal cortex — producing both the involuntary movements and the cognitive/behavioral changes.
Dopamine imbalance contributes: relative dopamine excess in the early phase drives chorea; dopamine depletion in the late phase contributes to rigidity and akinesia.

Cognitive and Psychiatric Mechanisms

Frontostriatal circuit disruption produces a subcortical dementia pattern: impaired executive function (judgment, planning, decision-making), attention deficits, and reduced processing speed — distinct from Alzheimer disease, which primarily affects memory. HD patients lose the ability to organize and sequence tasks before they lose factual memory.
Psychiatric symptoms — depression, irritability, apathy, obsessive-compulsive behaviors, psychosis — arise from disruption of limbic circuits through the basal ganglia. Depression and suicide risk are disproportionately high, even before motor symptoms appear.

Signs and Symptoms

Early Stage (Hyperkinetic Phase)

Chorea: Involuntary, irregular, purposeless jerky or writhing movements of the limbs, trunk, and face — the hallmark sign; movements appear dance-like and flow from one body part to another; the term "chorea" derives from the Greek word for dance
Subtle personality changes — irritability, mood swings, apathy, social withdrawal; often noticed by family before the patient
Cognitive slowing — difficulty with multitasking, planning, and organizing; impaired judgment and decision-making
Fidgetiness, clumsiness, balance difficulties; patients may initially be mistaken for intoxicated
Depression — present in ~40% of patients; significant suicide risk (4–6 times the general population)

Middle Stage (Mixed Phase)

Chorea peaks approximately 10 years after onset and begins to coexist with emerging rigidity and dystonia
Pronounced gait disturbance — wide-based, lurching, with frequent falls; the single greatest injury risk
Dysarthria — increasingly slurred, slow, and poorly coordinated speech
Dysphagia — difficulty managing food and saliva; aspiration pneumonia risk increases significantly
Progressive cognitive decline — inability to work, manage finances, or live independently
Behavioral changes intensify — impulsivity, aggression, paranoia, obsessive behaviors

Late Stage (Hypokinetic Phase)

Rigidity and bradykinesia replace chorea — the patient becomes increasingly akinetic and rigid, superficially resembling advanced Parkinson disease
Severe dystonic posturing — sustained involuntary muscle contractions distort the skeletal frame over time
Complete dependence for all activities of daily living; bedbound
Severe dysphagia — aspiration pneumonia is the leading cause of death
Mutism or near-total loss of speech
Cognitive decline to severe dementia; emotional awareness may persist longer than verbal or motor capacity

Juvenile Huntington Disease

Onset before age 20; typically inherited from the father (anticipation phenomenon — paternal CAG expansion)
Presents with rigidity and bradykinesia rather than chorea (the Westphal variant)
Seizures (uncommon in adult-onset HD)
Rapid cognitive decline; more aggressive course; shorter survival

Assessment Profile

Subjective Presentation

Chief complaint: Variable by stage — early: "I can't sit still," "I've been clumsy and dropping things," family reports personality changes; middle: "I keep falling," "I can't swallow properly," "I can't concentrate"; late: patient may be unable to communicate; caregiver describes rigidity, pain, and complete dependence
Pain quality: Deep muscular aching from sustained involuntary contractions and dystonic posturing; joint pain from repetitive abnormal movements and falls; late-stage rigidity produces constant cramping discomfort
Onset: Insidious onset typically between ages 35–50; genetic testing may have preceded symptoms by years; family history of HD is almost always present (autosomal dominant); progressive worsening without remission
Aggravating factors: Stress and anxiety significantly worsen chorea; fatigue increases involuntary movements; emotional distress amplifies psychiatric symptoms; stimulating environments (noise, crowds) increase agitation
Easing factors: Relaxation and calm environments reduce chorea temporarily; sleep abolishes chorea; structured routines reduce anxiety-driven worsening; seated or supported positions reduce fall risk
Red flags: Acute dysphagia with coughing/choking on food → aspiration risk; medical referral. New-onset seizures in adult patient → rule out secondary cause. Suicidal ideation → immediate psychiatric referral; do not dismiss. Sudden rigidity or altered consciousness → neuroleptic malignant syndrome if on antipsychotic medication → emergency referral.

Observation

Local inspection: Involuntary choreiform movements visible at rest — irregular jerking of limbs, facial grimacing, tongue protrusion; in late stage, dystonic posturing of hands, feet, and trunk; muscle wasting from disuse and malnutrition in advanced disease
Posture: Trunk instability from involuntary movements; compensatory wide stance for balance; late-stage skeletal distortion from chronic dystonic contractions — thoracic kyphosis, hip and knee flexion contractures, equinus deformity
Gait: Characteristic "dancing" gait — wide-based, lurching, with involuntary trunk and limb movements superimposed on voluntary walking; frequent stumbling and near-falls; in late stage, unable to ambulate

Palpation

Tone: Early stage — intermittent involuntary contractions superimposed on relatively normal baseline tone. Muscles feel as though they are "firing randomly." Middle stage — coexisting choreiform contractions and emerging dystonic rigidity. Affected muscles alternate between involuntary contraction and relative relaxation. Late stage — sustained rigidity predominating. Muscles feel boardlike and resistant to passive movement, similar to the lead-pipe rigidity of Parkinson disease but without the cogwheel quality.
Tenderness: Deep aching tenderness in muscles subjected to chronic involuntary contraction — shoulder girdle, cervical paraspinals, hip adductors, and hamstrings are commonly affected; trigger points develop in muscles chronically overactivated by choreiform or dystonic patterns; tenderness in joints subjected to repetitive abnormal loading (hips, knees) from falls and gait disturbance
Temperature: No temperature changes specific to HD; affected extremities maintain normal temperature unless secondary complications (immobility, circulatory compromise) develop in late stage
Tissue quality: Early stage — muscle bulk is relatively preserved. Muscles feel "jumpy" with intermittent involuntary twitching during palpation. Middle stage — progressive muscle wasting begins. Fascial restrictions develop in chronically contracted segments. Late stage — severe atrophy from disuse and malnutrition. Fibrotic changes in dystonic muscles. Contracted tendons palpable at ankles, knees, and wrists.

Motion Assessment

AROM: Profoundly disrupted by involuntary movements — the patient cannot perform smooth, controlled voluntary motion; choreiform jerks interrupt and override intended movements; in early stage, range may be mechanically full but functionally impaired; in late stage, dystonic contractures physically limit range at hips, knees, ankles, and wrists
PROM / end-feel: Early stage — full PROM with normal end-feel, but the examiner must contend with involuntary resistance from choreiform contractions (not true spasticity — it is intermittent and non-velocity-dependent). Late stage — firm/leathery end-feel from dystonic contractures and fibrotic changes; joint restrictions develop at hips, knees, and ankles
Resisted testing: Unreliable in the presence of chorea — involuntary movements confound the ability to maintain a sustained isometric contraction; strength may be relatively preserved in early stage but difficult to accurately assess; progressive weakness in middle and late stages from both disuse and neuronal loss

Special Test Cluster

HD is diagnosed by genetic testing (CAG repeat count on chromosome 4). The MT assessment cluster focuses on staging the movement disorder, screening for fall risk and dysphagia, and monitoring for psychiatric red flags.

Test	Positive Finding	Purpose
Romberg's test (CMTO)	Increased sway or loss of balance with eyes open (cerebellar/basal ganglia) or worsened with eyes closed (proprioceptive)	Screen for balance impairment and fall risk; positive in most HD patients by middle stage
Tandem gait (heel-to-toe walk) (CMTO)	Inability to maintain heel-to-toe line; involuntary lateral deviations; requires examiner spotting for safety	Assess gait coordination and fall risk; highly sensitive for basal ganglia dysfunction
Deep tendon reflexes (CMTO)	Variable — may be normal, hyperactive, or show frontal release signs (grasp reflex, palmomental reflex)	Screen for UMN involvement as disease progresses; helps stage neurological deterioration
Finger-nose-finger test (supplementary)	Dysmetria — overshooting or undershooting the target; involuntary movements superimposed	Assess coordination and cerebellar involvement; worsening performance tracks disease progression
Oral motor screening (supplementary)	Involuntary tongue movements, difficulty protruding tongue on command, drooling	Screen for bulbar involvement and aspiration risk; guides positioning during treatment

Staging note: Assess chorea severity and type at each visit. If rigidity is replacing chorea, the patient is transitioning from the hyperkinetic to hypokinetic phase — treatment approach must shift from calming techniques (reduce chorea) to mobility preservation (prevent contracture).

Differential Diagnoses

Condition	Key Distinguishing Feature
Parkinson Disease	Resting tremor (pill-rolling), bradykinesia, cogwheel rigidity — hypokinetic from onset; no chorea; no autosomal dominant inheritance pattern
Sydenham Chorea	Childhood onset following streptococcal infection (rheumatic fever); self-limiting; no cognitive decline; negative genetic testing
Tardive Dyskinesia	Drug-induced (antipsychotic medications); primarily orofacial movements; history of neuroleptic use; no cognitive decline; resolves with medication adjustment
Wilson Disease	Autosomal recessive copper metabolism disorder; Kayser-Fleischer rings on slit-lamp exam; liver disease; treatable with chelation therapy; onset typically before age 40
Benign Hereditary Chorea	Non-progressive chorea without cognitive decline; onset in childhood; normal life expectancy; negative HTT gene test

CMTO Exam Relevance

CMTO Appendix category A4 (neurological conditions)
Autosomal dominant inheritance is the defining genetic feature — 50% chance of transmission; complete penetrance above 40 CAG repeats; exam questions test understanding of inheritance patterns
Anticipation phenomenon: successive generations may have earlier onset and greater severity due to CAG repeat expansion, particularly through paternal transmission — a frequently tested genetic concept
Know the two-phase motor progression: early hyperkinetic (chorea) → late hypokinetic (rigidity) — treatment implications change with the phase
Basal ganglia pathology = involuntary movement disorder; distinguish from cerebellar pathology (ataxia, dysmetria) and UMN pathology (spasticity, hyperreflexia)
Subcortical dementia pattern (executive dysfunction, not memory loss) distinguishes HD from Alzheimer disease on exam
Suicide risk is a critical awareness point — 4–6 times the general population rate
Know that genetic testing is definitive but raises ethical issues (presymptomatic testing in at-risk individuals)

Massage Therapy Considerations

Primary therapeutic target: secondary muscle tension from chronic involuntary movements (early/middle stage) or dystonic contractures (late stage); compensatory postural overload; and psychosocial stress reduction — relaxation directly reduces chorea intensity because stress is a major aggravating factor
Phase-dependent approach: Early/middle stage — calming, rhythmic techniques to reduce involuntary movement intensity; avoid stimulating techniques (rapid percussion, brisk tapotement) that may amplify chorea through increased arousal. Late stage — contracture prevention and comfort care; gentle sustained stretching and positioning to maintain joint mobility in the face of progressive rigidity.
Safety — involuntary movements: The client cannot control choreiform movements. Secure the treatment environment — remove objects that could be knocked over; ensure the client cannot roll off the table; the therapist must be prepared for sudden unexpected limb movements without reacting with alarm
Cognitive and psychiatric considerations: If the client becomes disoriented, confused, or agitated, touch may be perceived as threatening — stop and reassess; proceed only if the client feels safe and consents. Behavioral disinhibition (impulsivity, inappropriate responses) is a neurological symptom, not a personal choice — respond with professional calm.
Dysphagia awareness: In middle and late stages, aspiration risk is significant. Do not position the client fully supine if swallowing is impaired — semi-reclined or side-lying with head elevated is safer. Have suction or the ability to call for help if choking occurs.
Contraindications: stimulating techniques that increase arousal and worsen chorea; deep tissue work in severely atrophied muscles; prone positioning in patients with swallowing difficulty; treatment during acute psychiatric crisis

Treatment Plan Foundation

Clinical Goals

Reduce overall arousal and involuntary movement intensity through parasympathetic activation
Maintain joint mobility and prevent contracture progression in chronically affected segments
Address secondary muscle pain from sustained involuntary contractions
Provide safe, supportive human contact that reduces psychological distress

Position

Side-lying preferred in middle and late stages — provides stability, prevents aspiration risk, allows access to trunk and extremities
Semi-reclined (45-degree) for clients who are agitated or have significant chorea — seated positions feel more secure than lying flat
Bolstering must be secure — involuntary movements can shift standard bolsters; use firm positioning supports
Padded side rails or treatment table with raised edges for safety in patients with significant chorea

Session Sequence

Slow, rhythmic effleurage to posterior trunk — establish a calming sensory input; consistent rhythm and predictable strokes reduce neurological arousal; allow involuntary movements to settle with sustained gentle contact
Gentle sustained compression to cervical paraspinals and upper trapezius — address chronic tension from head/neck choreiform movements; sustained holds are calming; avoid rapid or percussive techniques
Slow myofascial release to shoulder girdle — release fascial restrictions from chronic involuntary upper extremity movements; long sustained strokes following fascial lines
Hip adductor and hamstring release — gentle sustained compression and slow stripping to muscles affected by choreiform or dystonic patterns; [late stage: focus on contracture prevention with sustained end-range stretching]
Gentle passive ROM to major joints — hips, knees, ankles, shoulders, wrists — maintain available range; slow, predictable movements; accommodate involuntary resistance without forcing [late stage: this becomes the primary treatment focus]
Scalp and facial massage — if tolerated, gentle rhythmic contact to the scalp and temporal regions provides profound relaxation and may temporarily reduce facial choreiform movements
Closing effleurage — return to the same slow, rhythmic strokes used at the start; allow a gradual transition out of treatment rather than an abrupt stop

Adjunct Modalities

Hydrotherapy: Warm applications to chronically contracted muscles (no Uhthoff's concern in HD); moist heat to hip girdle and shoulder girdle pre-treatment to improve tissue pliability; warmth enhances the calming effect of treatment; avoid cold applications that may increase muscular rigidity or startle the patient
Joint mobilization: Gentle passive mobilization of hips, knees, and ankles to maintain joint play; Grade I–II oscillatory movements may have a calming neurological effect through rhythmic proprioceptive input; late-stage contractures may limit available glide — work within available range; do not force
Remedial exercise (on-table): Active-assisted ROM if the client can participate — therapist guides movement through available range while the client contributes voluntarily; purpose is proprioceptive input and mobility maintenance; do not attempt resisted exercise — involuntary movements make controlled resistance unsafe and unreliable

Exam Station Notes

Demonstrate awareness of the two-phase motor presentation — state whether the client is in the hyperkinetic or hypokinetic phase and how this changes your approach
Show safe treatment environment setup — secure bolstering, awareness of involuntary movements, no sharp objects within reach
If swallowing difficulty is reported, demonstrate appropriate positioning (side-lying, head elevated) and state the aspiration risk rationale
Document and verbalize any changes in movement pattern between sessions — chorea transitioning to rigidity indicates disease progression

Verbal Notes

Safety and involuntary movements: "I know your body moves on its own sometimes. That's completely fine — I'm ready for it and it won't bother me at all. If I need to move my hands, I will, and we'll continue."
Cognitive check-in: maintain simple, clear verbal cues throughout; if the client appears confused or distressed — "We can stop anytime. You're safe. Would you like to continue?"
Emotional distress: HD clients may cry, laugh, or display emotions unexpectedly (pseudobulbar affect or emotional lability) — "It's okay to feel whatever you're feeling. We can pause or keep going, whatever you prefer."
Post-treatment: "You may feel more relaxed for several hours. That's the goal. If you notice your movements get worse later today, let me know and we'll adjust next time."

Self-Care

Daily gentle stretching of hip flexors, hamstrings, and ankles — sustained holds (not ballistic) to slow contracture development; caregiver-assisted if the client cannot perform independently
Stress reduction strategies — guided breathing, meditation, or calming music; reduced chorea intensity in low-stress environments is well documented
Fall prevention — remove throw rugs, install grab bars, wear supportive footwear; the most common source of injury in ambulatory HD patients
Maintain social engagement and structured daily routines — routine reduces anxiety and cognitive burden; isolation worsens depression and suicide risk

Key Takeaways

Huntington disease is autosomal dominant with complete penetrance — every carrier of 40+ CAG repeats will develop the disease; the anticipation phenomenon means successive generations may have earlier and more severe onset
The basal ganglia (caudate nucleus and putamen) are selectively destroyed, producing chorea through loss of inhibitory GABAergic output to the thalamus
The disease progresses from a hyperkinetic phase (chorea) to a hypokinetic phase (rigidity and akinesia) — treatment approach must shift accordingly
Stress significantly worsens chorea; relaxation-focused massage is therapeutically indicated and directly reduces involuntary movement intensity
Suicide risk is 4–6 times the general population — practitioners must be aware of the client's psychological state and know referral pathways
Cognitive decline follows a subcortical pattern (executive dysfunction, not memory loss) — distinguish from Alzheimer disease
Dysphagia and aspiration pneumonia are the leading causes of death — positioning during treatment must account for swallowing impairment