Hyposmia in Parkinson's disease


Email: vikki.alvarez@yahoo.com

CURRENT TREATMENTS FOR Parkinson's disease (PD) are levodopa, dopamine agonists, monoamine oxidase–B (MAO-B) inhibitors, catechol-o-methyltransferase (COMT) inhibitors, anticholinergics, and surgical interventions to improve motor symptoms, such as tremor and rigidity. However, the effects on non-motor PD symptoms require further studies. Hyposmia is a common non-motor symptom of PD with a reported prevalence of 75–97%.1 The MAO-B inhibitor rasagiline is approved for use as monotherapy or adjunctive therapy in levodopa-treated PD patients with motor fluctuations. We added rasagiline (Azilect) to ongoing dopaminergic therapy for PD patients in our clinic to improve their motor fluctuations. With an interest in hyposmia, we decided to evaluate if our patients' olfaction would change with rasagiline treatment.

Seventeen patients already receiving PD medications were prescribed rasagiline, 1 mg/day, to improve their motor symptoms. Baseline motor symptoms were scored using the Unified PD Rating Scale (UPDRS; part III). Baseline olfaction was also measured using the University of Pennsylvania Smell Identification Test (UPSIT). Patients with other causes of hyposmia, such as asthma, nasal disease, and smoking history, were excluded. Mean baseline UPDRS-III score was 19.9 (±6.1) and UPSIT score was 19.0 (±10.0), indicating significant hyposmia (perfect score is 40). The patients were scheduled for a 3-month follow up, and on examination, 82% of them showed motor improvement, though the change from baseline UPDRS-III score at 3 months was not statistically significant (−0.88 ± 2.18, P = 0.14). Interestingly, median UPSIT scores at 3 months of rasagiline treatment were significantly improved compared with baseline (2.06 ± 3.44, P = 0.013).

UPSIT, while a sensitive and easily accessible tool, is not routinely used to monitor effects of PD treatment, even though progressive neuronal degeneration in the anterior olfactory region has been implicated in the neuropathology of PD hyposmia.2 To our knowledge, this is the largest case series reporting olfactory improvement using rasagiline as monitored by changes in UPSIT scoring. Long-term data from the TVP-1012 in Early Monotherapy for Parkinson's Disease Outpatients (TEMPO) study3 and results of the Attenuation of Disease Progression with Azilect Given Once-daily (ADAGIO) study4 suggest rasagiline has potential disease-modifying effects. It is tempting to speculate that improvement or stabilization of our patients' UPSIT scores reflects this potential disease-modifying effect of rasagiline in addition to its symptomatic effects.