Early Parkinsonism: Distinguishing Idiopathic Parkinson’s Disease from Other Syndromes

Rigidity is characterized as the presence of increased resistance to passive stretch throughout the range of motion [13]. “Lead pipe” rigidity remains sustained throughout the motion of the joint, while “cogwheel” rigidity is intermittent through the movement. The examiner must take care to distinguish between true rigidity and other forms of increased tone such as spasticity (a velocity dependent increase in tone) and paratonia (a resistance to passive motion created by the patient). Subtle rigidity can be enhanced in a limb by having the patient perform a voluntary movement of the contralateral limb [14]. Rigidity in early IPD is also asymmetric and most commonly found in the upper extremities, but it can be seen in the neck and lower extremities as well. Patients may initially complain of shoulder pain and stiffness that is diagnosed as rotator cuff disease or arthritis, when this pain is actually due to rigidity from Parkinson’s disease [15]. Severe axial rigidity out of proportion to appendicular rigidity, however, should suggest an alternate diagnosis in the early stages of the disease (such as progressive supranuclear palsy which is further discussed below).

Bradykinesia refers to decreased amplitude and speed of voluntary motor movements. This sign can be found throughout the body in the form of hypometric saccades, decreased blink rate, decreased facial expressions (“masked facies”) and softening of speech (hypophonia) [16]. Patients may initially report a general slowing down of movements as well as difficulty with handwriting due to their writing becoming smaller (micrographia) [17]. Bradykinesia is evaluated by testing the speed, amplitude, and rhythmicity of voluntary movements such as repetitive tapping of the thumb and first finger together, alternation of supination and pronation of the forearm and hand, opening and closing the hand and tapping the foot rhythmically on the floor. The examiner should also evaluate for generalized bradykinesia by viewing the patient rise from a seated to standing position as well as observing the patient’s normal speed of ambulation and speed and symmetry of arm swing.

Gait disturbance and postural instability can sometimes be found in early IPD; however, significant impairment of postural reflexes, gait impairment and early falls may point to a diagnosis other than IPD. Early IPD postural changes include mild flexion of the neck or trunk that may be accompanied by a slight leaning to one side. On examination of natural gait, the patient may exhibit asymmetrically reduced arm swing, slowing of gait and turning, shortened stride length and intermittent shuffling of the feet. With disease progression, all of these become more severe and there may be festination of gait (“hurried” gate with increased cadence and difficulty stopping). This can lead to instability and falls as the patient’s center of balance is displaced forward. Freezing of gait can also develop, but is rarely found in early IPD [18]. Postural stability is evaluated by the “pull test” where the patient is asked to stand in a comfortable stance with eyes open and feet apart and instructed to resist falling backwards when pulled by the examiner. The patient is allowed to take one step backwards with either foot if necessary to prevent falling. This test is usually normal in early IPD, but it often becomes abnormal with disease progression.