Dizziness is a common but poorly understood symptom in PSP.  That word can mean at least three things:

• a lightheadedness that seems a prelude to fainting, usually caused by a drop in blood pressure
• a sensation of movement of the body or the environment (usually spinning, but sometimes rocking or gliding)
• a vague sensation of being off balance. 

Impairment of autonomic function is common in the Parkinsonian disorders such as Parkinson’s disease, dementia with Lewy bodies and multiple system atrophy (in ascending order of likelihood).  There’s less evidence for, and research on, autonomic dysfunction in PSP. 

As background: The autonomic system is divided into sympathetic and parasympathetic portions.  Generally, the sympathetic system performs “fight or flight” functions such as raising blood pressure and heart rate in response to stress and the parasympathetic the “vegetative” functions such as powering the intestines to digest food.  When the sympathetic portion is damaged by a neurodegenerative disease, the most common symptom is lightheadedness upon standing.  We’ve all experienced this to a mild degree, but when severe, the result can be fainting, falls and injuries.

A well-designed project reported in the current issue of an obscure journal called The Polish Journal of Neurology and Neurosurgery has now compared PSP with PD and MSA with regard to various aspects of autonomic function including drops in blood pressure upon standing, or “orthostatic hypotension.”  The authors are Drs. Jakub Malkiewicz and Joanna Siuda of the Medical University of Silesia, in Poland.  (Disclosure: One of the two co-editors of the journal is an old friend and colleague of mine, Dr. Zbigniew Wszolek of the Mayo Clinic Jacksonville, who has special expertise in the atypical Parkinsonisms.)

The blood pressure was recorded in a very careful, standardized way:  It was measured after 15 minutes flat on a tilt table and then 5 minutes after being raised to a 60-degree angle.  The result was that none of the 25 patients with PSP or 20 healthy, age-matched controls experienced systolic blood pressure drops of more than 20 points.  However, this did occur in 20 (26%) of the 76 patients with PD and in 7 (58%) of the 12 with MSA.

This result is consistent with my own experience, where an office version of this test in my patients with early or moderate PSP experiencing dizziness rarely elicited much drop in blood pressure or intensification of the symptom.

How can this guide the care of people with PSP?  It means a few things:

• In people with early PSP, the possibility of low blood pressure is highly unlikely as a cause of dizziness.
• If the neurologist can rule out an inner-ear disturbance by the absence of a sensation of movement, nausea, a change in hearing, or a rhythmic, abnormal eye movement called nystagmus.  That leaves the possibility of a brain disturbance – either the PSP itself or an unrelated issue with the balance mechanism.
• A neurologist whose patient with known PSP reports dizziness should provide the same careful assessment as anyone else with the same symptom, rather than simply to diagnose low blood pressure due to dehydration or an excessive dosage of antihypertensive medication. 

A “brain disturbance” causing vague dizziness could be things like:

• a chronic subdural hematoma from a fall (which could be drained surgically)
• a minor stroke (which could prompt the addition of stroke prevention measures and a workup for treatable arterial narrowing)
• a small tumor (which could potentially be removed or irradiated)
• the effects on the brain of a medication (which could be reduced or discontinued)
• unusual seizures (which could be prevented with medication) – the most distant possibility

Nevertheless, in someone with advanced PSP (not the group studied by Malkiewicz and Siuda), it’s also important to seriously consider hypotension as the cause of dizziness.  Here’s why:

• When you can’t swallow comfortably or get up for a glass of water on on your own, it’s easy to become dehydrated.  
• Limiting fluids to avoid nighttime incontinence or bathroom trips can do the same. 
• Dopamine-enhancing drugs for Parkinson’s prescribed for PSP can reduce the blood pressure. 
• Some drugs for urinary incontinence can do the same by dilating the blood vessels. 
• Diabetes, even if undiagnosed, can damage the sympathetic nerves (“autonomic polyneuropathy”). 
• Diuretics prescribed for swollen ankles can reduce blood pressure.

Sorry to give you all these things to worry about, but use them to question your doctors about whether they’re doing everything they can to diagnose and maybe treat your dizziness.

My thanks to Drs. Malkiewicz and Siuda for directing our attention to this still-understudied issue.