Parkinson's Disease: Diagnosis
Although Parkinson’s disease is a specific, well-defined disease that can be reliably diagnosed at autopsy, it is defined in life solely by clinical criteria. This means the diagnosis rests entirely on the information (history) the patient provides and the findings of the physical examination. A doctor may recommend tests to rule out other disorders that might look like PD, but there is no test to diagnose PD.  This means we can never be 100% certain that we’ve diagnosed someone correctly.

That being said, we look for certain core features during examination, as well as a supportive history. For example, PD is slow in onset, so if a patient said that she woke up one morning with tremors and a shuffling walk, but had been playing competitive tennis the evening before, we’d think that she more likely had a brain infection or had taken a medication with bad side effects.

PD generally presents slowly, with progressive changes developing over months. For example, a patient may experience one or more of the following changes:

• Intermittent tremors (usually in the hands or jaw)
• Overall sluggishness or a sense of slowing down in general
• Difficulty getting out of a car seat or a low, soft sofa
• Softening of the voice
• Smallness and slowing of handwriting
• Change in posture and facial expression

Very often something is only noticed on a particular day, but friends and family will generally report that although they didn’t notice particular changes, now that they know what to look for, the changes began months or even years before.

During examination, we look for: tremor at rest, rigidity, slowness and loss of spontaneous movement, stooped posture and a characteristic gait.

Tremor
With Parkinson’s disease, tremor occurs primarily at rest. This means that the tremor goes away when the limb is moving but returns when the limb relaxes completely. The tremor is usually asymmetric, affecting one side more than the other, or affecting only one side. The fingers and hands are the body parts most commonly affected, followed by the jaw. The legs and feet may also be affected, but less so. In fact, virtually any body part can be affected by tremor, including the tongue, eyebrow, and lips.

The tremor usually disappears during sleep, but increases during periods of stress and excitement, after exercise, and in the cold. It may be present all the time, or only very occasionally. It may sometimes affect one hand and sometimes both. During times of relaxation it may completely disappear. It always disappears when the limb is moving.

Sometimes patients will describe having a tremor at home, but not have it in the office. This is uncommon, but does occur. In such circumstances the doctor cannot rely on the patient’s report because the nature of the tremor is important, and not all tremors are due to PD.  

Rigidity
Patients with PD have some degree of stiffness or rigidity in their joints. It most commonly appears in the wrists and neck, but may be present everywhere. The patient may feel stiff, but not always. During examination, the doctor will move the patient’s limbs to test for stiffness in the wrists, elbows, fingers, neck, and legs. A normal person’s joints move like well-oiled machine parts, but someone with PD will have a resistance to the movement, even though the person is relaxed. This resistance often, although not always, has a ratchet-like quality to it, called “cogwheel rigidity” because the movement feels like a cogged wheel moving.

Absence of Movement or “Akinesia”
Akinesia means “absence of movement” and refers to the absence or reduction of normal spontaneous activity. PD patients are like statues—they tend to not move. They blink less than others, swallow less, and have fewer movements like touching their face, scratching their nose, and shifting positions in their chair. This is one of the causes for the “staring” expression and the “masked facial expression” of PD patients. It is also the cause for drooling (inadequate swallowing).

Slowness or "Bradykinesia"
Bradykinesia means “slowness of movement” and is one of the main causes of disability in PD. PD patients move slower than others. They have reduced dexterity, particularly in their fingers so it takes a long time to button, zipper, manipulate small objects, put a screw into the wall, get money out of a wallet, etc. As one patient described it, “My left hand is fine, but I have to tell my right hand what to do. That slows me down a lot.” Patients sometimes have to consciously will an action that used to happen automatically, without thinking. If you had to “tell” your hand what to do to comb your hair, and guide each of its movements, it would take a lot longer than it should. This is what happens in PD. This also keeps PD patients from being able to do two things at the same time, another source of slowness. 

Gait and Posture
The word “gait” refers to how you walk. PD patients tend to become stooped. When they walk they don’t swing their arms, or they swing them less than normal. They tend to walk with their foot hitting the ground flatly, rather than having their heel hit the ground first. The distance between the feet, as they take steps, tends to decrease, and the speed of walking diminishes as well. The heel may scuff the floor. When they turn, they tend to take a few steps rather than pivoting (rotating on one foot).

Balance is impaired so that when knocked off balance, the PD patient may take several steps to keep from falling, or simply lose balance and fall, if not caught. The standard exam for PD has the patient pulled from behind for a balance check. The doctor is prepared to catch the patient.

Other features that are common in PD but are not considered “core” or “cardinal” features are: changes in voice, penmanship, sleep. The voice may become soft. Many patients develop a stutter, or develop an increased rate of speaking, despite having difficulty being understood. Penmanship, in addition to becoming slow and sometimes shaky, also becomes small. There are many sleep problems that develop in PD, but the one that is most indicative of a diagnosis of PD is “REM sleep disorder,” a condition in which patients may act out their dreams, kicking, punching, yelling while asleep.

In thinking about the above, it is important to keep in mind one very important underlying principle of brain function. Each part of the brain has a particular function, so that if you damage a particular location in the brain, it will cause a very specific change in the person’s function. It doesn’t matter how that part of the brain is damaged, whether from a stroke, a tumor, a bullet wound or an infection. This is one of the reasons we can’t always be sure that the diagnosis is PD. We can state that the particular part of the brain that is damaged in PD is affected, but we may be wrong about the process that is the cause. There are several different disorders that look very much like PD. Early on it may be impossible to tell if a patient has PD or some closely related disorder. This is especially true in elderly patients, since many of the normal changes that occur with age, may look like PD.

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