Pure Akinesia with Gait Freezing

Pure Akinesia with Gait Freezing

Introduction

Pure Akinesia with Gait Freezing (PAGF), also known as primary freezing of gait, is a rare progressive neurological disorder characterized by the sudden, transient inability to initiate movement, particularly while walking. It is considered a variant of atypical parkinsonism and represents one of the clinical phenotypes of progressive supranuclear palsy (PSP)[@factor2006][@gilman2008].

PAGF was first described as a distinct clinical entity in 2006 by Factor and colleagues, who identified patients with progressive gait freezing who did not meet criteria for Parkinson's disease (PD) or other known parkinsonian disorders. The condition is now recognized as part of the PSP spectrum, with many patients eventually developing classic PSP features[@williams2009].

Epidemiology

• Incidence: Rare; estimated 1-5% of parkinsonian disorders
• Age of onset: Typically 60-75 years
• Progression: Slowly progressive over 5-15 years
• Sex distribution: Slight male predominance reported in some series

Clinical Presentation

Core Symptoms

The hallmark feature of PAGF is freezing of gait—a sudden, transient cessation of forward movement despite the intention to walk. Patients describe their feet as feeling "glued to the floor"[@nutt2011].

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Pure Akinesia with Gait Freezing

Introduction

Pure Akinesia with Gait Freezing (PAGF), also known as primary freezing of gait, is a rare progressive neurological disorder characterized by the sudden, transient inability to initiate movement, particularly while walking. It is considered a variant of atypical parkinsonism and represents one of the clinical phenotypes of progressive supranuclear palsy (PSP)[@factor2006][@gilman2008].

PAGF was first described as a distinct clinical entity in 2006 by Factor and colleagues, who identified patients with progressive gait freezing who did not meet criteria for Parkinson's disease (PD) or other known parkinsonian disorders. The condition is now recognized as part of the PSP spectrum, with many patients eventually developing classic PSP features[@williams2009].

Epidemiology

• Incidence: Rare; estimated 1-5% of parkinsonian disorders
• Age of onset: Typically 60-75 years
• Progression: Slowly progressive over 5-15 years
• Sex distribution: Slight male predominance reported in some series

Clinical Presentation

Core Symptoms

The hallmark feature of PAGF is freezing of gait—a sudden, transient cessation of forward movement despite the intention to walk. Patients describe their feet as feeling "glued to the floor"[@nutt2011].

Primary features:

• Freezing of Gait (FOG): Sudden, episodic inability to step forward
• Akinesia: Reduced spontaneous movements, particularly in the lower extremities
• Start Hesitation: Marked difficulty initiating the first step
• Turn-Freezing: Freezing specifically when attempting to turn
• Festination: Progressive shortening of steps during walking

Associated features:

• Postural instability: Frequent falls, often backward
• Reduced arm swing: Bilateral rather than unilateral
• Facial masking: Reduced facial expression
• Speech changes: Hypophonia (soft speech), dysarthria

Progression

PAGF typically follows a predictable pattern:

Initial phase (1-3 years): Isolated gait freezing with minimal other features

Middle phase (3-7 years): Development of other parkinsonian features

Late phase (7-15 years): Evolution into classic PSP or other disorders

Approximately 50-70% of PAGF patients eventually develop classic PSP features, particularly vertical gaze palsy and axial rigidity[@mahapatra2004].

Pathophysiology

Neuropathology

PAGF is associated with neurodegenerative changes characteristic of PSP-type tauopathy:

• [Tau](/proteins/tau) pathology: 4-repeat tau deposits in:
• Brainstem nuclei (pedunculopontine nucleus, colliculi)
• Basal ganglia
• Cerebral [cortex](/brain-regions/cortex)
• Nigrostriatal degeneration: Loss of dopaminergic [neurons](/entities/neurons) in substantia nigra
• Brainstem involvement: Particularly the pedunculopontine nucleus (PPN), critical for gait initiation

Neural Circuitry

The freezing of gait in PAGF involves dysfunction in multiple neural networks:

| Region | Role | Dysfunction in PAGF |
|--------|------|---------------------|
| Pedunculopontine Nucleus | Gait initiation | Tau deposition, neuronal loss |
| Basal Ganglia | Motor sequencing | Dopaminergic denervation |
| Supplementary Motor Area | Motor planning | Reduced activation |
| Frontal Cortex | Executive function | Executive deficits |

Neuroimaging Findings

• MRI: May show midbrain atrophy ("hummingbird sign") in later stages
• DaTscan: Reduced dopamine transporter uptake in striatum
• FDG-PET: Hypometabolism in brainstem and frontal regions
• DTI: White matter tract damage affecting gait networks

Diagnosis

Clinical Criteria

Proposed diagnostic criteria for PAGF:

Essential:

• Progressive gait freezing for >1 year
• No significant tremor at rest
• No sustained levodopa response
• No other cause for freezing

Supportive:

• Falls within 2 years of onset
• Vertical gaze palsy (late)
• Axial rigidity
• Dysphagia

Differential Diagnosis

PAGF must be distinguished from other causes of gait disturbance[@postuma2015]:

| Condition | Key Distinguishing Features |
|-----------|----------------------------|
| Parkinson's Disease | Tremor, asymmetric onset, sustained levodopa response |
| Progressive Supranuclear Palsy | Vertical gaze palsy, early falls, axial rigidity |
| Normal Pressure Hydrocephalus | Urinary incontinence, cognitive decline |
| Vascular Parkinsonism | Stepwise progression, cerebrovascular lesions |
| Drug-Induced Parkinsonism | Temporal relation to dopamine blockers |
| Functional Neurological Disorder | Inconsistent examination findings |

Diagnostic Workup

• Neurological examination: Document freezing triggers, response to cueing
• MRI brain: Rule out structural lesions, assess for atrophy
• DaTscan: Confirm dopaminergic deficit
• Levodopa challenge: Document (lack of) response
• Neuropsychological testing: Assess cognitive profile

Treatment

Pharmacological Management

Limited efficacy is a hallmark of PAGF:

| Medication | Typical Response |
|------------|-------------------|
| Levodopa/Carbidopa | Minimal to partial benefit in ~30% |
| Dopamine agonists (pramipexole, ropinirole) | Variable, often limited |
| MAO-B inhibitors (selegiline, rasagiline) | Modest benefit in some |
| Amantadine | May reduce freezing episodes |
| Clozapine | Low-dose may help akinesia |

Non-Pharmacological Approaches

Physical Therapy is the cornerstone of management[@keus2014]:

• Gait training: Intensive treadmill training
• Balance exercises: Fall prevention strategies
• Strength training: Maintain lower extremity strength
• Flexibility exercises: Reduce rigidity

Cueing Strategies can bypass freezing:

• Visual cues: Lines on floor, laser pointers
• Auditory cues: Metronome, rhythmic counting
• Tactile cues: Light touch on back or leg

Assistive Devices:

• Quad cane or walker for safety
• Weighted walker for stability
• Hip protectors to reduce fracture risk

Surgical Interventions

• Deep Brain Stimulation (DBS): Target is typically the PPN or STN
• Limited evidence for PAGF specifically
• May help some patients with combined PSP
• Risks include worsening cognition

Prognosis

Disease Course

• Median survival: 7-12 years from symptom onset
• Functional decline: Progressive, with eventual need for assistive devices
• Cause of death: Often pneumonia, falls, or complications of immobility

Prognostic Factors

Poor prognosis:

• Early falls
• Early cognitive impairment
• Poor response to levodopa
• Rapid progression of freezing

Relatively better prognosis:

• Late onset
• Isolated freezing for many years
• Dopa-responsive features

Research Directions (2024-2026)

Emerging Therapies

• Tau-targeting agents: Anti-tau antibodies and small molecules in development
• Neuroprotective strategies: Targeting neuroinflammation
• PPN stimulation: Refined DBS targets for gait disorders
• Stem cell therapy: Experimental approaches

Biomarker Development

• [Neurofilament light](/biomarkers/neurofilament-light-chain-nfl) chain (NfL): Prognostic biomarker
• Tau PET imaging: In vivo tau burden assessment
• Gait analysis: Quantitative freezing detection

Recent Research Highlights

• [Autopsy case of PSP presenting as PAGF](https://pubmed.ncbi.nlm.nih.gov/40399058/) (2025): Neuropathological correlation
• [Dopa-responsive tremor in PSP](https://pubmed.ncbi.nlm.nih.gov/39135248/) (2025): Phenotypic variation

See Also

• [Progressive Supranuclear Palsy](/diseases/progressive-supranuclear-palsy)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Atypical Parkinsonism](/diseases/corticobasal-degeneration)
• [Freezing of Gait](/mechanisms/freezing-of-gait)
• [Tauopathies](/mechanisms/tauopathies)
• [Pedunculopontine Nucleus](/brain-regions/pedunculopontine-nucleus)

External Links

• [National Institute of Neurological Disorders and Stroke](https://www.ninds.nih.gov/)
• [Parkinson's Foundation - Freezing of Gait](https://www.parkinson.org/)
• [CurePSP - Foundation for PSP|MSA|CBD](https://www.psp.org/)

References

[Factor SA, et al., Pure akinesia with gait freezing: a clinical entity. Neurology. 2006;67(8):1518-1522 (2006)](https://doi.org/10.1212/01.wnl.0000245478.71216.5b)

[Gilman S, et al., Second consensus statement on the diagnosis of multiple system atrophy. Neurology. 2008;71(9):670-676 (2008)](https://doi.org/10.1212/01.wnl.0000310575.70901.40)

[Unknown, Williams DR, Lees AJ. Progressive supranuclear palsy: clinicopathological concepts and diagnostic challenges. Lancet Neurol. 2009;8(3):270-279 (2009)](https://doi.org/10.1016/S1474-4422(09)

[Nutt JG, Bloem BR, Giladi N, et al., Freezing of gait: moving forward on a mysterious clinical phenomenon. Lancet Neurol. 2011;10(8):734-744 (2011)](https://doi.org/10.1016/S1474-4422(11)

[Unknown, Mahapatra RK, Edwards MJ, Schott JM, Bhatia KP. "Pure akinesia" as a feature of progressive supranuclear palsy. Mov Disord. 2004;19(3):365-369 (2004)](https://doi.org/10.1002/mds.10667)

[Postuma RB, Berg D, Stern M, et al., MDS clinical diagnostic criteria for Parkinson's disease. Mov Disord. 2015;30(12):1591-1601 (2015)](https://doi.org/10.1002/mds.26424)

[Keus SHJ, Munneke M, Graziano M, et al, European Physiotherapy Guideline for Parkinson's Disease (2014)