Olfactory Function in Patients With and Without Temporal Lobe Resection

In the December 2012 issue of the journal, Epilepsy and Behavior, Drs. Haehner and colleagues from the Smell and Taste Clinic of the Department of Otorhinolaryngology at the University of Dresden Medical School in Dresden, Germany; the Saxonian Epilepsy Center in Radeberg, Germany; and the Department of Neurology at the University of Dresden Medical School in Dresden, Germany, set out to assess smell outcome from epilepsy surgery that is rarely if ever reported in most epilepsy surgery evaluations. The study looked at smell function in patients with temporal lobe epilepsy before and after resection of temporal lobe structures and addressed the question as to whether there are any significant differences in the ability to smell as a function of the side of the surgery that was performed to stop seizures.

The investigators evaluated 13 individuals pre- and 22 postoperative patients and 35 age and sex-managed healthy controls who underwent olfactory testing by means of a Sniffin’ Sticks testing device, which is a measurement of threshold discrimination and identification abilities for smell function. The researchers found that patients with unilateral epileptic focus but without a temporal lobe operation tended to have impaired abilities to identify smells compared to those individuals without epilepsy. There were no significant differences in smell function on the same side of where the focus of the seizures are coming from as compared to the non-affected side; however, patients after temporal lobe resection presented with significantly impaired bilateral discrimination and identification abilities compared to healthy controls and had lower scores for detecting smells on the side on which surgery was performed as compared to the non-operated side. The authors concluded that before an operation, smell or olfactory function is only partially impaired before the operation; however, after an operation, it can deteriorate on the same side of the lesion.

This study is important because it highlights a special sense that is often not discussed amongst epilepsy surgery evaluations and patients are likely not to report absence of smell; however, smell is linked to taste and taste was not evaluated in this particular patient and that would have more of an impairment on quality of life for those individuals who noticed a difference. Nevertheless, this study is helpful to those individuals who do detect a slight change in smell after an operation to at least allay their fear that this may be an expected finding after surgery.