Problems With Diagnosis

Diagnosis is difficult at every stage of the disease, but particularly in the early stages. No single test can provide a diagnosis. A diagnosis will likely involve physical and neurological examinations, conducted over time to assess changes in reflexes, coordination, muscle strength, and mental function. Your doctor might also see how you respond to medicine. • Parkinson's disease symptoms are different for different people. Some are hard for even doctors to detect. Others are obvious even to an untrained eye. • No blood test, brain scan or other test can be used to make a definitive diagnosis of Parkinson’s disease. At present the diagnosis of PD relies on observation of a patient’s movement by a trained specialist (typically a neurologist) as the patient executes movement tasks such as walking to and fro, tapping their fingers or performing rapidly alternating hand movements – there is no objective, precise, definitive test in use today. You may be familiar with the visible signs of someone with PD. The three ‘cardinal’ motor symptoms are: • Stiffness (rigidity): muscle stiffness detected by a doctor on examination • Slowness (bradykinesia): decrease in spontaneous and voluntary movement; may include slower walking, less arm swinging while walking, or decreased blinking or facial expression • Resting tremor: a rhythmic, involuntary shaking that occurs in a finger, hand or limb when it's relaxed and disappears during voluntary movement Not everyone with Parkinson's experiences all three motor symptoms, but slowness always is present. And although tremor is the most common symptom at diag - nosis, only 70% or so of all people with Parkinson's have tremor (Figure 1) Other motor symptoms - walking problems or difficulty with balance and coordination - may also occur. These can happen any time in the course of Parkinson's, but are more likely as the disease advances. Assessment of PD symptoms is usually done by a neurolo - gist employing rating scales such as the Unified Parkinson’s Disease Rating Scale or ‘UPDRS’, which is based on observations and judgments by them of the presenting patient. However, the use of this and similar clinical scales are inherently subjective and require considerable clinical experience. With regard to PD, many symptoms are imprecise, particularly in its early stages, and also common to other diseases, both neurodegenerative and non-neurodegenerative in nature, with the result that PD is commonly either misdiagnosed or the diagnosis is missed completely. A UK study back in 2012 found that diagnoses by primary care doctors had a correct diagnosis of just 53% and specialists who were not movement disorder experts had a correct diagnosis rate of only 75%. In contrast, movement disorder specialists were mistaken by only 6% to 8%, which raises an obvious issue – in order to be referred on to a movement specialist, the patient’s general practitioner (GP) must first recognize and diag - nose the symptoms. A more recent review looked at the PD diagnostic accuracy over the last 25 years, and found that it is still not satisfactory and has not improved over that period, particularly for patients in the early stages of the disease. By the time that PD is diagnosed currently, the disease is already well advanced, significant dopaminergic neuron loss and damage has already occurred, and any possibility of delaying further disease progression and neuroprotec - tion is unlikely. In the coming years, it is likely that drugs will become available to slow, or even halt, the disease progression, so the goal must be to diagnose and treat PD well before the irreversible destructive changes have taken place, ideally at least 5 years earlier than is currently the case (Figure 2).