Approach to tremor: Clinical sciences

Tremor refers to an involuntary, rhythmic, oscillatory movement due to the actions of opposing muscles, which is most commonly observed in the upper extremities. It could also be present in other parts of the body, including the lower extremities, head, jaw, and trunk. The pathophysiology of tremor includes multiple neural pathways, such as those involving the basal ganglia, premotor and motor cortices, thalami, and cerebellum. The most common causes of tremor include Parkinson disease, cerebellar dysfunction, essential tremor, and enhanced physiologic tremor.

Now, if a patient presents with chief concerns suggesting tremor, you should first obtain a focused history and physical examination. Patients typically report shaky hands, which can often cause difficulty performing tasks such as eating or writing. Sometimes, they might report shaking in other parts of the body, as well as a family history of a tremor. On examination, you might observe involuntary, rhythmic, oscillatory movements in the hands and possibly shaking of other parts of the body, for example, the head. With these findings, you can diagnose a tremor.

Your next step is to find the cause, so first assess for a medication-induced tremor. If your patient is taking a medication with a known side effect of tremor, such as lithium, valproic acid, amiodarone, β-adrenergic agonists like albuterol, or anti-psychotics with anti-dopaminergic activity like haloperidol, the likely diagnosis is a medication-induced tremor.

Here’s your first clinical pearl! Patients with a medication-induced tremor can experience tremors at rest, known as a rest tremor, or with action, known as an action tremor. Sometimes, the tremors can be accompanied by parkinsonism with rigidity and bradykinesia. Finally, when the offending drug is discontinued the tremors will stop.

On the flip side, if your patient does not report taking medications associated with tremor, the next step is to assess for a rest tremor. Alright, if the rest tremor is present, you should consider Parkinson disease. The patient will typically report the shakiness of their hands at rest, with one hand worse than the other. They will also report slowness of movement and, in some cases, frequent falls.

On exam, you will observe a hand tremor at rest, with movements that look like they are rolling a pill between their thumb and index finger, known as a pill-rolling tremor. The tremor will improve with action, meaning when they move their arms or hands. There will also be bradykinesia, which is slowness of movement and decrease in amplitude or speed with continued movement, as well as rigidity. Additionally, you may observe facial masking, which refers to an impaired facial expression in response to emotion. Next, if you passively move a limb around a joint in a circular motion, you might feel a series of stops or stalls, which is called cogwheeling or cog-wheel rigidity. Finally, you might notice a shorter stride length or stooped posture. With these findings, diagnose Parkinson disease.

Time for another clinical pearl! Parkinson-plus syndromes are characterized by similar signs and symptoms as Parkinson disease, including a rest tremor. However, they include additional features such as early-onset dementia, psychosis and hallucinations, and severe dysautonomia. Additionally, you might notice gaze palsy and alien limb phenomenon, in which your patient reports that their limb feels “disconnected” and controlled by someone else. Parkinson-plus syndromes include dementia with Lewy bodies, progressive supranuclear palsy, multiple system atrophy, and corticobasal degeneration.

Now, let’s discuss the scenario where the rest tremor is absent. In this case, your next step is to assess for cerebellar signs. First, look for non-physiologic nystagmus at resting or endgaze, and impaired saccades when the patient rapidly shifts their gaze between two objects. Next, you might find dysdiadochokinesia, which is the inability to perform rapid alternating movements, such as during rapid alternating supination and pronation of the hands.

On finger-nose-finger and heel-to-shin testing, you might find dysmetria, which is the inability to perform smoothly coordinated and targeted movements. For example, on the finger-nose-finger test, they might point past the finger as they are unable to judge the distance properly. This is referred to as past-pointing. Last but not least, you might see gait ataxia, which is characterized by a wide-based, unsteady gait with truncal instability and inconsistent stride length. If these signs are present, diagnose cerebellar dysfunction as the cause of the tremor, which can occur as a result of traumatic brain injury, brain tumor, multiple sclerosis, stroke, or even genetic conditions, like spinocerebellar ataxia.