Article
Evaluating volumetric MRI quantification of the olfactory bulb as an independent factor correlating the outcome of idiopathic normal pressure hydrocephalus after shunt implantation
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Authors
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Dino Podlesek
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Carl-Gustav-Carus, Dresden, Deutschland
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Johannes Gerber
- Abteilung Neuroradiologie, Universitätsklinikum Carl-Gustav-Carus, Dresden, Deutschland
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Gabriele Schackert
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Carl-Gustav-Carus, Dresden, Deutschland
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Matthias Kirsch
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Carl-Gustav-Carus, Dresden, Deutschland
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Thomas Hummel
- Klinik und Poliklinik für Hals-, Nasen- und Ohrenheilkunde, Arbeitsbereich „Riechen und Schmecken“, Universitätsklinikum Carl-Gustav-Carus Dresden, Deutschland
| Published: | September 16, 2010 |
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Outline
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Objective: The cardinal symptoms of idiopathic normal pressure hydrocephalus (iNPH) are gait disturbance, dementia and incontinence. An important pathological feature is dysfunctional CSF dynamics. Examination of the CSF has shown the neuronal degeneration in patients with iNPH. Surgical treatment is usually the implantation of a ventriculo-peritoneal shunt (VPS) system. Ventricle size does not necessarily correlate with clinical improvement after shunting. The purpose of the present study is to evaluate the olfactory bulb (OB) volume as an indicator of neuronal affection in iNPH.
Methods: The prospective study includes 24 patients with iNPH (9 women and 15 men, mean age=68 y). Two patients. suffered from obstructive HCP secondary to aqueduct stenosis. A group of otherwise healthy controls included 7 women and 10 men (mean age of 61y). Comprehensive assessment of olfactory function was performed with the "Sniffin’ Sticks" test kit. Cranial MRI and sniffing tests were performed before and three months after operative treatment of the hydrocephalus via VPS. However, due to decreased patients’ compliance, postoperative evaluation of the olfactory function was performed in only 10 patients. OB volume was measured by coronal t2-weighted MR images with a slice thickness of 2 mm.
Results: Pre- and postoperative measurements of the olfactory bulb could be completed in 15 pts. Preoperative OB volume in patients (n=24) with iNPH were significantly smaller compared to healthy controls (average value of OB volume: 48 vs 60ccm, p=0,018 in right OB, p=0,016 in left OB). There was a postoperative increase in volume of the olfactory bulbs. There was no correlation with other radiological parameters. Despite the reduced volume of the OB in iNPH, there was no significant reduction in olfactory function.
Conclusions: Although the ventricle size may be persistent, the olfactory bulb increases in size after successful neurosurgical treatment. Olfactory bulb volume may present an objective parameter for clinical outcome correlation in patients with iNPH. However, larger patient groups are necessary to determine the significance of this finding. The olfactory bulb may present an easily quantifiable structure to measure morphological regeneration.
