Neurologists Often Misdiagnose Drug-Induced Parkinsonism

["M.Schild" <mmoo@xxxxxxxxxxxxxxxx>]

Failure of recognition of drug-induced parkinsonism in the elderly 
CD Esper, SA Factor
Movement Disorders 2008;23:401-404

Drug-induced parkinsonism (DIP) is often misdiagnosed in elderly patients, 
even by neurologists, and may lead to years of inappropriate treatment, 
according to this study.

The authors performed a chart review of 354 patients with newly identified 
parkinsonism presenting to a movement disorders clinic over a two-year 
period. DIP was considered in patients with subacute onset of at least 2 of 4 
cardinal motor features of PD that began while the patient was on a dopamine 
blocking agent. Agents raising suspicion included typical antipsychotics, 
atypical antipsychotics, and metoclopramide. 

Of 354 patients presenting with parkinsonism, 24 (6.8%) patients met the 
criteria for DIP. Drugs responsible included:

Atypical antipsychoticsÂ11
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂOlanzapineÂÂÂÂÂÂ6
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂRisperidoneÂÂÂÂÂ3
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂAripiprazoleÂÂÂÂ2

MetoclopramideÂÂÂÂÂÂÂÂÂÂ5
Typical antipsychoticsÂÂ2
Antipsychotic plus meto.ÂÂÂÂÂÂÂÂ2
AmoxapineÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ2

Only 1 patient arrived with the correct diagnosis from the referring center, 
although 7 more had discontinued the offending medication. PD was diagnosed 
by the referring center in 11 cases, and were receiving anti-PD treatment. 
Three patients were being treated for essential tremor. Nineteen of 24 
patients had been seen by a neurologist prior to referral. Time to diagnosis 
of DIP averaged 1.8 years.

Seventeen patients were followed after cessation of the offending medication. 
Results showed:
ConditionÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂNÂÂÂÂÂÂÂmean duration of follow-up
Total remissionÂÂÂÂÂÂÂÂÂ10ÂÂÂÂÂÂ10.1 months
Significant improvementÂ3ÂÂÂÂÂÂÂ8.6 months
Modest improvementÂÂÂÂÂÂÂÂÂÂÂÂÂÂ3ÂÂÂÂÂÂÂ13.2 months
No changeÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ1ÂÂÂÂÂÂÂ9 months

The potential for a protracted recovery may be underrecognized, the authors 
say. Prior to referral, 1 patient had discontinued medication for 2 weeks, 
but with no change in his condition, he was diagnosed with PD.

The authors note the following features that may raise the suspicion of DIP:
.ÂÂÂÂÂÂÂSubacute onset
.ÂÂÂÂÂÂÂBilateral symptoms from the outset
.ÂÂÂÂÂÂÂOrofacial dyskinesias
.ÂÂÂÂÂÂÂPrior or current treatment with a dopamine blocking agent
.ÂÂÂÂÂÂÂResting tremor is not an exclusion criterion

"Recent studies have demonstrated that [atypical antipsychotics] definitely 
worsen parkinsonism in PD, and it is clear from our study and others that 
these drugs can also be a primary cause of parkinsonism," the authors note. 

An E-MOVE report on the ability of atypical antipsychotics to cause 
parkinsonism is archived HERE.


http://www.mdvu.org/emove/article.asp?ID=847