A 56-year-old woman is evaluated for a 1-year history of tremor. The tremor is more prominent on the right side. She also reports increasing problems with balance and numerous falls, especially when arising from a chair or turning. The patient does not have any significant cognitive symptoms. She has occasional urinary incontinence, intermittent constipation, and a history of acting out of dreams during sleep.
On physical examination, blood pressure is 115/75 mm Hg sitting and 85/70 mm Hg standing, pulse rate is 65/min sitting and 75/min standing, and respiration rate is 22/min. Bruises over the upper and lower extremities secondary to falls are present. On cranial nerve examination, dysmetric saccades, decreased facial expression, and hypophonic speech are noted. Vertical eye movements are normal. A low-amplitude tremor at rest that is more prominent on the right side is present. Repetitive finger tapping movements are bradykinetic. On finger-to-nose testing, mild dysmetria is present. Gait is ataxic with a wide base and frequent veering to both sides; she is unsteady on turning. Gait speed is normal, but arm swing is decreased. A pull test confirms postural instability. No sensory deficits are noted.
Which of the following is the most likely diagnosis?
A. Multiple system atrophy
B. Parkinson disease
C. Progressive supranuclear palsy
D. Vascular parkinsonism
MKSAP Answer and Critique
The correct answer is A: Multiple system atrophy.
The combination of parkinsonism, cerebellar ataxia, and early postural instability and falls in this patient is most consistent with multiple system atrophy (MSA), a Parkinson-plus syndrome. MSA (Shy-Drager subtype) also can be associated with prominent autonomic deficits, such as orthostatic hypotension and urinary symptoms. Her history of acting out of dreams during sleep (rapid eye movement sleep behavior disorder [RBD]) is another clue suggestive of a synucleinopathy (such as Parkinson disease or MSA). Patients with MSA are at higher risk for falls, dysautonomia, and sleep-related complications, including nocturnal stridor.
Many of this patient’s symptoms also can occur in idiopathic Parkinson disease, but her early prominent imbalance, recurrent falls, and cerebellar features are atypical for this disorder.
Progressive supranuclear palsy is the main differential diagnosis, given the patient’s early prominent postural instability. She does not, however, have the characteristic impairment in vertical extraocular movements. Additionally, her cerebellar features, asymmetric tremor, hyposmia, and RBD are more typical of multiple system atrophy than progressive supranuclear palsy.
Patients with vascular parkinsonism have sudden or step-wise onset of symptoms and exhibit disproportionate involvement of the lower extremities. The involvement of the upper body, gradual course, and nonmotor symptoms in this patient make this diagnosis unlikely.
- The combination of parkinsonism, cerebellar ataxia, and early postural instability and falls is most consistent with a diagnosis of multiple system atrophy.
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