9 Parkinson’s disease

Introduction

Parkinson’s disease (PD) was first described by James Parkinson, the English physician after whom it was named, in his monograph on the ‘Shaking Palsy’ in 1817.¹ While it occurs in 0.3% of the general population this climbs to 1% of those 60+ years old² and up to 3% in patients aged at least 80 years.³

It is a progressive degenerative neurological disorder characterised by a tetralogy of symptoms, including tremor, rigidity, bradykinesia and postural instability.⁴ The pathological features are loss of dopamine-producing neurons from the substantia nigra in the brainstem and other brainstem nuclei,⁵ together with Lewy bodies (ubiquinated protein deposits in the cytoplasm of neurons) and Lewy neurites (thread-like proteinaceous inclusions in neurites).^6,⁷

Most general practitioners are less concerned with pathophysiology of the illness and much more concerned with diagnosis and treatment. What follows is a coalface clinician’s approach to diagnosing and treating PD. While the above provides a scientific backdrop to PD, the purpose of this chapter is to alert the general practitioner to proper management.

PD is diagnosed on the basis of history and examination, rather than any specific blood test.⁸ The 2006 United Kingdom clinical guidelines suggest that PD requires specialist confirmation of diagnosis and subsequent follow-up.⁹ While there is good argument for the involvement of a neurologist, PD is a chronic illness with a predictably progressive decline so optimal care dictates a partnership between the specialist and general practitioner. As with all chronic illnesses, ideal care must accommodate lifestyle factors, careers and demonstrate an empathic approach, which is the forte of the general practitioner who is often more closely aligned with the patient and the home environment.

While the exact cause is unknown, a variety of genes have been identified from PARK1 at locus 4 q21 ¹⁰ through to PARK13 at locus 2 p12¹¹ and the list is continuing to expand. This has special relevance when PD occurs in young patients, especially those younger than 50 years. It is hard to organise the tests in Australia but any condition with a potential genetic basis mandates discussion. The majority of cases of PD are sporadic and hence counselling will probably not alter the prevalence.

There was a major outbreak of Parkinsonism after the influenza epidemic (with encephalitis lethargica) in the early twentieth century, when lesions in the substantia nigra became apparent.¹² Nevertheless the role of environmental factors was not fully appreciated until the 1980s when MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), a by-product of synthetic opiate MPPP, a meperidine analogue designer drug, was reported to cause acute Parkinsonism in drug addicts in California.¹³ Since then it has been acknowledged that pesticides may cause Parkinsonism,^14,¹⁵ thus various potential toxins can be avoided.

One may also consider lifestyle issues thought to protect against PD, such as smoking or taking of Chinese green tea,^16,¹⁷ although smoking has sufficient other reasons to be avoided.

What follows is an idiosyncratic approach to the diagnosis and treatment of PD. It does not follow some of the rules endorsed by many ‘Parkinsonologists’ but after considerable clinical experience it has proven effective and is provided as one possible way to manage the disease.

Making the Diagnosis

As with all diagnoses in neurology, the diagnosis starts with a high index of suspicion and a detailed history. Often ‘the penny drops’ when calling the patient to come into the consultation. The patient is slow to respond to the call; has difficulty rising from the chair, especially if that chair is low; and will be slow to walk into the consultation room.

Critical observation will reveal that the patient has a paucity of movement, is somewhat bent forward rather than standing erect, and may take smaller steps than is usual for their age group. The face is often expressionless, looks younger than that of chronological peers, and there is reduced blinking. The patient often doesn’t swing both arms when walking (but may swing one arm) and appears to be shuffling along rather than taking discrete steps. The alternative may be the patient about to be called into the consultation room, seen sitting in the waiting room appearing to be somewhat bored, with a slow ‘pill rolling’ tremor of one hand. This seems to stop as soon as the patient realises it is their turn to see the doctor, and they may use that ‘shaking’ hand to push up from the chair to walk into the room and in so doing the ‘shaking’ stops.

It can be seen that in the classical case the diagnosis has been offered on a platter, even before the patient has entered the consultation room when the formal process is supposed to start. The corollary of this is that one has to be acutely aware of what is on the platter to realise that the diagnosis is being offered, otherwise it may be missed and rely on someone else to show superior clinical acumen.

Taking a History

Patients with PD will present with a number of initial complaints, which may be as vague as a feeling of ‘slowing down’ to a complaint of falling without cause, or of shaking. There are no prizes for diagnosing the classical case with the patient having the obvious Parkinsonian tremor and those features described above. Skill is required to tease out early cases, especially if one believes in early treatment, something that remains quite controversial but is a personal preference.

Once suspicion has been aroused, there is a series of mandatory questions to seek out the early symptoms that even the patient may not have identified without prompting. Patients with early PD may have trouble turning over in bed at night; they may have difficulty rising from a low sofa; or getting in or out of a car, especially a low-slung car such as a convertible. They may complain of difficulty initiating gait because they are afraid of falling over. Some may report falling when they turn quickly or losing their balance and being unable to regain stability, although they were able to do so previously. Symptoms of feeling stiff, which may translate as ‘feeling funny or heavy in the limbs’, may be confirmed if actively sought.

PD has been staged by Hoehn and Yahr ⁴ (see Table 9.1) as starting with unilateral symptoms and signs through to serious disability. As the condition progresses a patient may report speech changes with softer, monotonous speech, possibly complicated by excessive dribbling or drooling. Patients may have problems initiating gait, having what is called ‘inertia’. These patients may report that they cannot get started when they want to walk but once they get going they seem to gain speed, even starting to run without wanting to, and may have difficulty stopping. They might develop techniques to stop, such as selecting a fixed object like a wall and walking into it to slow down their centre of gravity that they have been chasing.

TABLE 9.1 The Hoehn and Yahr staging of Parkinson’s disease

Stage 1	Unilateral symptoms and signs
Stage 2	Bilateral symptoms and signs
Stage 3	Bilateral features with impaired postural reflexes causing disability
Stage 4	Severe gait disturbance though still able to stand and walk without aids
Stage 5	Inability to stand or walk without aids, wheelchair or bed-bound

Posture, being bent in the middle and unable to stand up straight, may be a major symptom. Writing may be difficult, either due to the imposition of the tremor or patients may report their handwriting has become smaller, veering up and off the horizontal, hence becoming difficult to read even without tremor.

Often the patient will present with the complaint of tremor and will suspect the diagnosis of PD. Benign essential tremor is far more common than is PD, and the patient will be greatly relieved if given this diagnosis. It is therefore important to have simple tools with which to compare the two most common causes of tremor (see Table 9.2). A patient with PD may have both an essential and a PD tremor.

TABLE 9.2 Differentiating Parkinsonian tremor from essential tremor

Characteristic	Parkinson’s disease	Benign essential tremor
Tremor location	Hands, legs, circumoral	Hands, head (titubation), voice
Laterality	Usually unilateral at onset	Usually bilateral
Bradykinesia	+	–
Rigidity	+	–
Family history	Usually –	+ in ≥ 50%
Effect of alcohol	–	+ (reduces tremor)
Age of onset	Usually > 60 years	Younger, ~40 years
Timing of tremor	At rest (when distracted)	With activity (rarely at rest)

More recently there has been a realisation that PD may be associated with symptoms that transcend the motor features. These include neuropsychiatric symptoms, sleep disorders (such as REM sleep behaviour disorder), autonomic symptoms and sensory symptoms.¹⁸ Impulsivity, increased gambling and antisocial behaviour have been associated with PD and its treatment.¹⁹ The term ‘punding’ with associated compulsive sequenced behaviour is associated with PD. Impotence is reported by up to 60% of men with PD.²⁰

It can be seen that there are many questions needing to be asked, both to assist with the diagnosis and with defining the extent of the illness and its impact on the patient’s life.

Examination

In the section above ‘Making the diagnosis’, many of the early features have already been described and should be apparent even before starting the formal consultation. From these findings and corroboration based on the history, the doctor can steer directly towards the signs to be displayed.

The tetralogy of principal features is well accepted (see Box 9.1) and available for examination. Working from the head downwards, the features include: positive glabellar tap (tapping the patient over the forehead above the bridge of the nose should only illicit three blinks—more than this is considered positive); paucity of blinking; difficulty with upward gaze; cog-wheeling of saccadic eye movements; decreased facial wrinkling with increased sebum in the skin, giving an oily appearance and looking younger than actual age; increased drooling; soft voice devoid of intonation; expressionless face; and possibly a posture with the head somewhat flexed forward. The patient may well have a positive palmar mental response (scratching the patient’s palm may elicit movement of the ipsilateral jaw, via the mentalis muscle) and is concurrent with other frontal lobe signs such as grasp reflexes.