A patient presenting with uncontrollable shaking of the body may automatically make you assume they have Parkinson’s disease. Although shaking is a classic sign of Parkinson’s, there are other movement disorders that include similar symptoms. Essential tremor affects about 10 million Americans, and Parkinson’s affects about 1 million. Telling these two conditions apart can be tricky, and diagnosis can take time.

According to a paper from American Family Physician, the first step in the evaluation of a patient with tremor is to categorize the tremor based on its activation condition, topographic distribution and frequency. The diagnosis of tremor is based on clinical information obtained from a thorough history and physical examination. For particularly difficult cases, single-photon emission computed tomography to visualize the integrity of the dopaminergic pathways in the brain may be useful to diagnose Parkinson’s disease.

The most common pathologic tremor is essential tremor. In about 70% of patients with Parkinson’s disease, tremor is the first presenting feature. This tremor is typically asymmetric, occurs at rest and becomes less prominent with voluntary movement.

Parkinson’s or essential tremor

Signs of essential tremor include:

• Shaking on both sides of the body
• Shaking that usually happens during activity, such as writing or eating
• Tremors without other symptoms
• Symptoms that vary in age of onset, intensity, duration, progression and resulting disability
• Shaking mainly in the hands, but can include head and voice tremor

There are several key ways essential tremor is different from Parkinson’s disease.

“In people with essential tremor, that’s really the main symptom,” said Justin T. Phillips, M.D., movement disorders neurologist with Norton Neuroscience Institute.

Signs of Parkinson’s disease include:

• Shaking mainly on one side of the body
• Shaking that happens when the body is at rest
• Slowness of movement (bradykinesia)
• Muscle rigidity and stiffness
• Average age of onset 60 years old; typically with increased disability over time
• Shaking occurring in the upper and lower extremities; usually not in the head

“Early signs of Parkinson’s and essential tremor can overlap,” Dr. Phillips said. “A patient can have both conditions, so it’s important to understand the differences in these disorders. People sometimes assume that if they shake at all, it’s Parkinson’s. That isn’t the case.”

When to refer

Depending on the patient’s personal and family medical history, severity and location of symptoms and any relevant lab results, physicians may continue to monitor symptoms or refer to neurology.

Existing low-amplitude tremor that does not interfere with daily life may need only a wait-and-see approach. The patient’s medication list should be evaluated for possible medication-induced tremor, and screening for hyperthyroidism is generally appropriate.

Tremor combined with other signs such as bradykinesia (slowness of movement) and rigidity (muscle stiffness) could suggest parkinsonism. Referral to neurology should be considered, but depends on the provider’s level of comfort with diagnosing and managing the condition. The extent to which the symptoms are causing trouble in the patient’s daily life also should be considered if you are thinking of referring out. Generally, further work-up (i.e., imaging) is not necessary and does not need to be completed prior to neurology evaluation.