Unidirectional Olfactory Hallucination Associated with Ipsilateral Unruptured Intracranial Aneurysm

Abstract

Summary: Purpose:We describe a patient with complex partial seizure with unidirectional olfactory aura associated with ipsilateral unruptured aneurysm. Methods and Results:The patient felt a sweet pleasant smell coming from behind her right side every time before the attack. Cranial magnetic resonance imaging (MRI) and threedimensional computed tomography (CT) angiography revealed a large aneurysm at the bifurcation of the right middle cerebral artery and compression of the right orbitofrontal cortex. Small spikes were recorded from the right orbitofrontal and superior temporal gyri and from the uncus by the cortical electrodes during clipping of the aneurysm.Conclusions: The orbitofrontal cortex may have a function related to the ipsilateral directional olfactory sensation. Key Words: Complex partial seizure-Unilateral olfactory auraUnmptured aneurysm-Orbitofrontal cortex.Unruptured intracranial aneurysm is one of rare causes of epilepsy. Daly ( 1 ) reported one in 55 patients with epilepsy with uncinate fits, and Currie et al. (2) had only one in 666 patients with temporal lobe epilepsy. Several other patients (3-7) associated with intracranial aneurysm were reported. Seizure types of most of the patients consisted of complex partial seizures and a few patients noticed a sensory aura.Olfactory aura was produced by Penfield and Jasper (8) on stimulation of the uncus and amygdala. Although functions of the secondary olfactory center are not"ful1y understood, olfactory aura may result from epileptic discharges in the secondary olfactory center.We report a patient with unilateral olfactory aura associated with unruptured cerebral aneurysm located in the ipsilateral orbitofrontal lobe. CASE REPORTA 49-year-old woman complaining of attacks of impaired consciousness was admitted to our hospital. In the past 6 months, she felt a sweet pleasant smell like flowers or sweet fruits as an aura, which she had not previously experienced. She clearly identified the direction of Accepted October I?, 1998. Address correspondence and reprint requests to Dr. M. Mizobuchi at Department of Neurology, Nakamura Memorial Hospital, Minami I , Nishi 14, Chuo-ku, Sapporo 060-8570, Japan. the smell, which always came from behind her right side, and never the left side or front, and never spread to left side or front. After a few seconds, she became confused. During the attack, she could respond verbally but could not remember recent events. After the attack, she could not recall what she had done. The longest attack lasted -20 min without generalized seizures. Automatism, visual or gustatory hallucinations, and d6ja vu were not present. There was no neurologic abnormality including olfaction. Interictal EEG showed paroxysmal discharges over the right temporal region.Cranial magnetic resonance imaging (MRI) showed a round flow-void lesion -I cm in diameter between the tip of the right temporal lobe and the orbitofrontal gyrus (Fig. 1). Three-dimensional computed tomography (CT) angiography revealed a large aneurysm at the bifurcation of th...

The olfactory system as the gateway to the neural correlates of consciousness

“…(Again, the bulb has been described as being functionally equivalent to the first-order relay of the thalamus; Kay and Sherman, 2007; see also Murakami et al, 2005.) This observation is consistent with findings from research on the neural correlates of various kinds of conscious olfactory experiences, including olfactory perceptions, olfactory imagery, and olfactory hallucinations (Markert et al, 1993; Mizobuchi et al, 1999; Leopold, 2002). This research, which includes neuroimaging studies (Henkin et al, 2000), experiments involving direct stimulation of the brain (Penfield and Jasper, 1954), and lesion studies (Mizobuchi et al, 1999), suggests that endogenic, olfactory consciousness does not require the olfactory bulb.…”

“…First, we discuss the role of the most peripheral anatomical structures: the olfactory epithelium and olfactory bulb. Regarding the latter, previous findings suggest that the olfactory bulb is unnecessary for endogenic olfactory consciousness (Mizobuchi et al, 1999; Henkin et al, 2000). (Again, the bulb has been described as being functionally equivalent to the first-order relay of the thalamus; Kay and Sherman, 2007; see also Murakami et al, 2005.)…”

Olfactory imagery: A review

“…Mizobuchi et al (1999) described an individual with an aneurysm in the anterior insular cortex that also affected the right orbitofrontal cortex (secondary olfactory cortex). This individual experienced pleasant, frequent, and brief OHs, redolent of flowers or sweet fruits.…”

EEG–fMRI findings in late seizure recurrence following temporal lobectomy: A possible contribution of area tempestas

“…Symptoms and signs were strongly suggestive of temporolimbic network involvement, and hyperkinetic features consistent with basal frontal recruitment [11] were never reported or observed. In addition, detailed questioning did not elicit any recollection of olfactory hallucinations, typical for seizures arising from the OC [12]. Third, preoperative MRI suggested and histopathology confirmed the presence of severe hippocampal sclerosis, and there was no MRI abnormality over the basal frontal region.…”