Physical examination of children with bradykinesia is important to determine the severity and location of rigidity, tremor, and bradykinesia. For adults, there is a Unified Parkinson's Disease Rating Scale (UPDRS) that is used to grade the severity and distribution of the disorder.

In some cases, this rating scale is also useful in children. Important elements of the child's history include the rate of disease progression, possibility of any trigger at its onset, possible toxins or medications, and any variation in symptoms during the day. In particular, variation of symptoms or the presence of dystonia suggests the possibility that the child may have dopa-responsive dystonia (DRD). DRD is a metabolically based, neurologic movement disorder that usually responds rapidly to treatment. Although it is rare to find a family history of parkinsonism in childhood-onset bradykinesia, the autosomal recessively inherited "parkin" gene mutation is more likely in families where there is a history of intermarriage within the same family (consanguinity).

Etiology

The causes of parkinsonism in children are different from those in adults, and thorough examination usually requires a careful search for metabolic as well as degenerative diseases.

Static (fixed) injury:
Post-infectious (e.g., encephalitis lethargica, Von Economo's disease), stroke

Degenerative:
Juvenile Parkinson's disease (autosomal recessive form is often caused by mutations in the Parkin gene), spinocerebellar ataxia, Huntington's disease (Westphal variant), Hallervorden-Spatz disease (neuronal brain iron accumulation type 1), Pelizaeus-Merzbacher disease, Machado-Joseph disease (SCA3), human immunodeficiency virus (HIV, AIDS)

Chemical/metabolic:
Dopa-responsive dystonia, tyrosine hydroxylase deficiency and other abnormalities of bioamine metabolism, abnormalities of folate metabolism, Wilson's disease, basal ganglia calcification (Fahr's disease)

Malformations:
Joubert syndrome, Dandy-Walker malformation, basilar impression, vermian agenesis, cerebellar dysgenesis, rhombencephalosynapsis, Chiari malformation (types 2 and 3), pontocerebellar hypoplasia

Drug-induced:
MPTP poisoning, rotenone, tetrabenazine, reserpine, methyldopa, sedatives, neuroleptics (e.g., olanzapine, quetiapine), anti-emetics, calcium-channel blockers, isoniazid, serotonin-reuptake inhibitors (e.g., sertraline, fluoxetine), meperidine

Disorders that mimic Parkinsonism:
Catatonia, depression, spasticity, hypothyroidism

Workup

It is important for the diagnosing physician to look for reversible or treatable causes of parkinsonism. If there is any possibility of exposure to a toxin,

An important element of the diagnosis is observing the changes in the symptoms with time.

heavy metal, carbon monoxide, or medication, this needs to be investigated. An MRI of the brain is important in order to look for a tumor or stroke. An MRI may also show if there is degeneration in other areas of the brain, such as the cerebellum or brainstem.

When there is difficulty differentiating juvenile Parkinson's disease from dopa-responsive dystonia, it may be helpful to perform a phenylalanine-loading test or lumbar puncture with measurements of dopamine and other neurotransmitters and metabolites. These tests may help to identify a specific metabolic disorder. An important element of the diagnosis is observing the changes in the symptoms with time, and response to treatment with L-DOPA.

Treatment

In some cases, if a specific metabolic disorder can be identified, a specific treatment may be available. However, the mainstay of treatment for parkinsonism of any cause is the use of oral L-DOPA. L-DOPA is a precursor of dopamine and is converted by the body into dopamine. Dopamine cannot be directly ingested, as it is poorly absorbed by the intestines and rapidly degraded in the blood. In order to deliver as much L-DOPA to the brain as possible, it is usually combined in a pill with another medicine such as carbidopa in the combined medication Sinemet®. Carbidopa inhibits the conversion of L-DOPA to dopamine until the L-DOPA has entered the brain. This increases the effectiveness of L-DOPA, thus lowering the oral dose and decreasing the side effects.

The side effects are mostly due to the L-DOPA that is converted to dopamine outside the brain. Side effects include nausea, diarrhea, and low blood pressure. In some cases, an increase in the carbidopa dose helps to counteract this. (Domperidone is an effective alternative but is not available in the United States.) Side effects are worse when taken on an empty stomach. Ondansetron may be helpful to treat nausea; however, many more common anti-nausea medicines, including metoclopramide (Reglan®), prochlorperazine (Compazine®), or meclizine (Antivert®) may actually worsen symptoms. L-DOPA is absorbed better when taken with carbohydrates and worse with proteins. If it is taken with a protein meal, the effects are decreased. Parkinson's disease typically requires increasing doses of L-DOPA over many years, and eventually side effects occur. In contrast, children with dopa-responsive dystonia often have complete resolution of symptoms on very low doses of L-DOPA, with no need to increase the dose over time. Exceptions to this have been reported.

Other medications used for parkinsonism include anticholinergics (trihexphenidyl, benztropine), dopamine agonists (pramipexole, ropinirole, bromocriptine, pergolide), amantadine, and entacapone. With the exception of the anticholinergics, there is limited experience with the use of these medications in children.