Initial Diagnosis of Parkinsonism Frequently Changes After Follow-Up
NEW YORK, November 14 (Reuters Health)—The precise etiology of what appears to be a parkinsonian disorder is not always clear when the symptoms first appear, and the diagnosis often changes over time, according to a paper in the November Journal of Neurology, Neurosurgery, and Psychiatry. Use of rigid research criteria does not necessarily help make the diagnosis.
“Accurate diagnosis of Parkinson’s disease is important both in clinical practice, where it will influence management, and in research, where the validity of findings may be compromised if studies include heterogeneous conditions,” Dr. Carl Counsell, of the University of Aberdeen, United Kingdom, and colleagues wrote.
The report describes 66 patients who were followed for at least one year after an initial diagnosis of “possible or definite parkinsonian syndrome.” After a median follow-up of 29 months, the clinical diagnosis had changed in 22 patients (33%). Most of the changes (82%) occurred in the first year. Reasons for the modified diagnoses included development of additional clinical features, early cognitive impairment and neuropsychiatric features, results of radiological imaging, poor response to levodopa, and lack of disease progression. More than a third of those who were misdiagnosed with Parkinson’s disease were eventually determined to have dementia with Lewy bodies.
As part of their study, the researchers retrospectively applied formal research criteria using records from patients’ baseline evaluation and latest yearly follow-up. In eight patients (12%), the latest clinical diagnosis differed from the research-based diagnosis.
“The major implication is that doctors making the diagnosis of a parkinsonian syndrome need to be aware of the potential inaccuracy of the initial diagnosis and be prepared to review patients regularly (probably at least yearly) and change it as appropriate,” Dr. Counsell said in an interview with Reuters Health. “A change in diagnosis may also require a change in treatment, either stopping unnecessary treatment or starting new treatment.
“This study needs to be replicated in a larger sample of patients and over a longer period of time to see if the diagnosis continues to change over time, both of which we are doing,” Dr. Counsell explained. “It would be also important to see if other centers have similar results to our own,” he noted.
J Neurol Neurosurg Psychiatry. 2008;79(11):1202-1207.
Cross-Sensitivity Rates Between Antiepileptic Drugs Are High
NEW YORK, November 21 (Reuters Health)—A paper in the November 4 Neurology confirmed that rates of cross-sensitivity between antiepileptic drugs (AEDs) are high and provided specific data to aid in estimating an individual patient’s risk.
Dr. Lawrence J. Hirsch and colleagues from New York’s Columbia University determined the incidence of AED-related rash in 1,875 outpatients with epilepsy treated with one or more of 15 common AEDs. Overall, 269 patients (14.3%) had a rash attributed to at least one AED, and 2.8% had a rash to two or more AEDs.
The authors saw evidence of specific cross-sensitivity between carbamazepine and phenytoin. Of 59 patients who had a rash to carbamazepine and who also received phenytoin, 57.6% had a rash to phenytoin. In 81 who had a rash to phenytoin and were also prescribed carbamazepine, the rate of rash was 42%.
The authors also observed specific cross-sensitivity between carbamazepine and phenobarbital, with a trend toward this effect between zonisamide and phenytoin.
In patients who developed rashes in response to one of the six most common drugs and were also prescribed another of these most common drugs, the highest cross-sensitivity rates were seen in patients given carbamazepine and then prescribed lamotrigine (20%), lamotrigine and then carbamazepine (26.3%), carbamazepine and then oxcarbazepine (33%), oxcarbazepine and then carbamazepine (71.4%), carbamazepine and then phenobarbital (26.7%), phenobarbital and then phenytoin (53.3%), phenytoin and then phenobarbital (19.5%), oxcarbazepine and then lamotrigine (37.5%), and lamotrigine and then oxcarbazepine (20%).
In patients who had an allergy with or without rash to a non-AED medication, significantly higher AED-rash rates were observed for carbamazepine (36% in subjects with a non-AED allergy vs 2.2% in those without), lamotrigine (16.1% vs 6.1%), and phenytoin (38.8% vs 7.9%).
Neurology. 2008;71(19):1527-1534.
Amyloid Deposition Does Not Necessarily Signal Cognitive Impairment in Elderly
NEW YORK, November 25 (Reuters Health)—In elderly people without clinically significant cognitive impairment, such as Alzheimer’s disease, amyloid deposition in the brain is not associated with worse cognitive function, University of Pittsburgh School of Medicine (UPMC), researchers reported in the November Archives of Neurology.
“The important implication,” Dr. William E. Klunk of UPMC told Reuters Health, “is that there is a window of time when the early pathology of Alzheimer’s disease can be detected years before the onset of symptoms, allowing an opportunity to treat the disease before extensive brain damage has occurred.”