Abstract
BackgroundComplications of idiopathic intracranial hypertension (IIH) are usually caused by elevated intracranial pressure (ICP). In a similar way as in the optic nerve, elevated ICP could also compromise the olfactory nerve system. On the other side, there is growing evidence that an extensive lymphatic network system around the olfactory nerves could be disturbed in cerebrospinal fluid disorders like IIH. The hypothesis that patients with IIH suffer from hyposmia has been suggested in the past. However, this has not been proven in clinical studies yet. This pilot study investigates whether structural changes of the olfactory nerve system can be detected in patients with IIH.Methodology/Principal FindingsTwenty-three patients with IIH and 23 matched controls were included. Olfactory bulb volume (OBV) and sulcus olfactorius (OS) depth were calculated by magnetic resonance techniques. While mean values of total OBV (128.7±38.4 vs. 130.0±32.6 mm3, p=0.90) and mean OS depth (8.5±1.2 vs. 8.6±1.1 mm, p=0.91) were similar in both groups, Pearson correlation showed that patients with a shorter medical history IIH revealed a smaller OBV (r=0.53, p<0.01). In untreated symptomatic patients (n=7), the effect was greater (r=0.76, p<0.05). Patients who suffered from IIH for less than one year (n=8), total OBV was significantly smaller than in matched controls (116.6±24.3 vs. 149.3±22.2 mm3, p=0.01). IIH patients with visual disturbances (n=21) revealed a lower OS depth than patients without (8.3±0.9 vs. 10.8±1.0 mm, p<0.01).Conclusions/SignificanceThe results suggest that morphological changes of the olfactory nerve system could be present in IIH patients at an early stage of disease.
Highlights
Idiopathic intracranial hypertension (IIH) is characterized by increased intracranial pressure (ICP) and is affecting mainly obese women of childbearing age
While mean values of all morphological parameters were nearly similar in both groups, Pearson correlation showed that patients with a shorter medical history of IIH revealed a smaller Olfactory bulb volume (OBV) (r = 0.53, p,0.01)
Compared with patients who suffered from IIH for more than one year (n = 15) the difference of total OBV failed to reach significance (116.6624.3 vs. 135.1643.6 mm3, p = 0.21) and there was no difference in number of reduced
Summary
Idiopathic intracranial hypertension (IIH) is characterized by increased intracranial pressure (ICP) and is affecting mainly obese women of childbearing age. Elevated intracranial pressure (ICP) is a characteristic feature of IIH and could damage the olfactory nerves (ONs) directly by mechanical impact. Giuseffi and colleagues reported that up to 25% of IIH patients complain about decreased smell [8] This assumption is clinically relevant, since undetected and untreated olfactory disorders are associated with reduced quality of life and problems with daily life situations [9,10]. There is growing evidence that an extensive lymphatic network system around the olfactory nerves could be disturbed in cerebrospinal fluid disorders like IIH. The hypothesis that patients with IIH suffer from hyposmia has been suggested in the past. This has not been proven in clinical studies yet.
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