MKSAP Quiz: 2-year history of tremor in the dominant right hand
A 41-year-old woman is evaluated for a 2-year history of tremor in the dominant right hand. She says that the tremor has begun interfering with her work as a hairdresser, especially when she uses scissors. She also reports tightness in the forearm. Following a physical exam and MRI, what is the most likely diagnosis?
A 41-year-old woman is evaluated for a 2-year history of tremor in the dominant right hand. She says that the tremor has begun interfering with her work as a hairdresser, especially when she uses scissors. She also reports tightness in the forearm. The patient is able to eat, write, and type without difficulty and has had no trauma, imbalance, slowness of movement, or change in gait speed. Alcohol has no effect on the tremor. There is no family history of tremor.
On physical examination, vital signs are normal. A right upper extremity tremor is noted, as are rhythmic flexion of the wrist, involuntary flexion of the fingers, and pronation of the forearm. The tremor is present both at rest and during action and resolves by changing the position of an outstretched arm. No dysmetria, dysdiadochokinesia, bradykinesia, rigidity, shuffling gait, or reduced arm swing is noted. Her handwriting is neither tremulous nor micrographic.
An MRI of the brain is unremarkable.
Which of the following is the most likely diagnosis?
A. Cerebellar tremor
B. Dystonic tremor
C. Essential tremor
D. Parkinson disease
E. Rubral tremor
MKSAP Answer and Critique
The correct answer is B. Dystonic tremor. This content is available to MKSAP 18 subscribers as Question 12 in the Neurology section. More information about MKSAP is available online.
This patient has a dystonic tremor, which occurs both at rest and with action and is characterized by associated dystonic posturing and the presence of a null point at which change in the position of the affected limb resolves the tremor. The null point is the position at which the trajectories of the forces caused by dystonic coactivation of agonist and antagonist muscles neutralize each other, which leads to resolution of the tremor. In addition, the action component of tremor has task specificity in that it is worse with use of scissors but spares the handwriting.
Cerebellar tremor is characterized by increasing tremor amplitude as the limb approaches the target (terminal intention tremor) and the presence of associated cerebellar symptoms. These features are absent in this patient.
Essential tremor is the most common movement disorder and often presents with a bilateral upper extremity postural and action tremor. It is not associated with dystonic features. Additional features include bilateral involvement and a positive family history. Amelioration of the tremor by ethanol is typical and did not occur in this patient.
Parkinsonian tremor is prominent at rest and can reemerge after a brief delay when the arms are held in an outstretched position. Although dystonia can be seen secondary to Parkinson disease, the absence of other associated features, especially the bradykinesia required for a diagnosis of Parkinson disease, excludes this diagnosis.
Rubral tremor is caused by focal injury to cerebellar outflow pathways and is characterized by a coarse tremor that is present at rest but most severe during action. This type of tremor has a prominent proximal component and interferes with various actions, such as feeding, typing, and writing, in a nonselective way. Also, MRIs of the brain reveal a focal causative lesion that is not present in this patient.
Key Point
- Dystonic tremor occurs both at rest and with action and is characterized by associated dystonic posturing and the presence of a null point at which a change in the position of the affected limb resolves the tremor.