Progressive Supranuclear Palsy

Progressive supranuclear palsy (PSP), also known as Steele–Richardson–Olszewski syndrome, is a late-onset neurodegenerative disease characterised by the gradual deterioration and death of specific brain areas. It leads to symptoms such as impaired balance, slowed movements, difficulty moving the eyes, and cognitive impairment.

PSP is often confused with Parkinson's disease, frontotemporal dementia, and Alzheimer's disease due to overlapping symptoms. The exact cause is unknown, but it involves the accumulation of tau protein within the brain.

A person with progressive dementia, ataxia, and incontinence. A clinical diagnosis of normal-pressure hydrocephalus was entertained. Imaging did not support this, however, and on formal testing, abnormal nystagmus and eye movements were detected. A sagittal view of the CT/MRI scan shows atrophy of the midbrain, with preservation of the volume of the pons. This appearance has been called the "hummingbird sign" or "penguin sign". Also, atrophy of the tectum is seen, particularly the superior colliculi. These findings suggest the diagnosis of progressive supranuclear palsy.

Signs and Symptoms

Initially, PSP presents with loss of balance, lunging forward while walking, bumping into objects, and frequent falls. Dementia symptoms are also common early on. Other early symptoms include changes in personality, general slowing of movement, and visual issues. Patients often show apathy, lack of inhibition, anxiety, and unease.

As the disease progresses, patients may experience dementia, slurred speech, difficulty swallowing, and difficulty moving the eyes, particularly in the vertical direction. This can result in difficulty reading and increased risk of falls. Other signs include poor eyelid function, facial muscle contracture, a backward-tilted head, sleep disruption, urinary incontinence, and constipation. Some patients maintain full cognitive function until late in the disease.

Visual symptoms are very important for diagnosis. Patients often have difficulty looking downwards, known as downgaze palsy, followed by upgaze palsy. Square-wave jerks and diminished vertical saccades are key diagnostic movements. Patients may also have convergence insufficiency, leading to double vision when reading. The characteristic facial appearance known as the procerus sign is diagnostic.

Cause

The cause of PSP remains unknown. Less than 1% of cases have a familial link. The H1 haplotype of the tau protein gene on chromosome 17 is associated with PSP, but the presence of this variant alone is not sufficient to cause the disease. Other genetic and environmental factors are under investigation. Mitochondrial dysfunction and exposure to mitochondrial complex I inhibitors (like acetogenins and rotenoids) have also been implicated.

Pathophysiology

PSP affects neurons and glial cells, leading to neurofibrillary tangles (NFTs) of tau protein. These tangles differ chemically from those seen in Alzheimer's disease. Affected brain areas include the basal ganglia, brainstem, cerebral cortex, cerebellum, and spinal cord. Some researchers consider PSP, corticobasal degeneration, and frontotemporal dementia variations of the same disease.

Diagnosis

Magnetic resonance imaging (MRI) is commonly used to diagnose PSP, often showing atrophy in the midbrain with preservation of the pons, known as the "hummingbird" sign.

Types

PSP is categorised into several subtypes based on pathological findings:

• Classical Richardson syndrome (PSP-RS)
• PSP-parkinsonism (PSP-P) and PSP-pure akinesia with gait freezing (PSP-PAGF)
• Frontal PSP, PSP-corticobasal syndrome (PSP-CBS), PSP-behavioural variant of frontotemporal dementia (PSP-bvFTD), and PSP-progressive non-fluent aphasia (PSP-PNFA)
• PSP-C
• PSP induced by Annonaceae

Differential Diagnosis

PSP is often misdiagnosed as Parkinson's disease due to similar motor symptoms. However, tremor is rare in PSP, and eye movement abnormalities are absent in Parkinson's. Early falls, upright posture, and poor response to levodopa also differentiate PSP from Parkinson's. PSP can also be misdiagnosed as Alzheimer's disease.

Management

Treatment

There is no cure for PSP. Management is supportive, with some short-term response to levodopa and amantadine. Botox can treat neck dystonia and blepharospasm. Rivastigmine and zolpidem have shown promise in small studies for cognitive and motor symptoms, respectively.

Rehabilitation

Patients benefit from occupational therapy, speech-language pathology, and physical therapy. Robot-assisted gait training and balance exercises are often used. Mobility aids like weighted walkers are recommended to prevent falls. As the disease progresses, patients may need wheelchairs and assistance with daily activities.

Prognosis

PSP has a poor prognosis, with average survival of seven years from symptom onset. Pneumonia, often due to aspiration, is a common cause of death.

Self-assessment MCQs (single best answer)

What is the characteristic sign seen on MRI imaging for Progressive Supranuclear Palsy?

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Which protein accumulates in the brain in Progressive Supranuclear Palsy?

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Which eye movement abnormality is most commonly associated with Progressive Supranuclear Palsy?

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Which of the following is NOT a common early symptom of Progressive Supranuclear Palsy?

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Which haplotype of the tau protein gene on chromosome 17 is associated with PSP?

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Which of the following treatments is used for neck dystonia and blepharospasm in PSP patients?

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Which subtype of PSP is characterised by classical symptoms including early falls and vertical gaze palsy?

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What is the average survival time from symptom onset for PSP patients?

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What is a common cause of death in patients with Progressive Supranuclear Palsy?

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Which of the following is a key diagnostic movement abnormality in PSP?

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