Does This Patient Have Parkinson Disease or Essential Tremor?

In the elderly patient with tremor, the differential diagnosis is usually between essential tremor (ET) and Parkinson disease (PD). A careful history and examination are the keys to the diagnosis. Essential tremor is a bilateral action tremor of the upper limbs whereas PD begins unilaterally and is a rest tremor. A handwriting sample can usually distinguish PD from ET as the former is small (micrographic) but atremulous whereas writing in ET is tremulous but normal sized. In ET, there are no signs aside from tremor but in PD, the tremor is accompanied by bradykinesia and rigidity.