Marked olfactory impairment in idiopathic intracranial hypertension.
OBJECTIVE
Many long-duration astronauts develop signs of elevated intracranial pressure and have neuro-ophthalmological findings similar to idiopathic intracranial hypertension (IIH) patients. Some also present with nasal congestion and subjective olfactory impairment. We prospectively evaluated olfactory function in IIH patients and the effect of 6° head-down tilt, which simulates the headward fluid shifting in microgravity, as spaceflight analogues.


METHODS
Olfaction was tested for all subjects in upright and 6° head-down tilt positions using two different measures: University of Pennsylvania Smell Identification Test and Olfactory Threshold Sniffin' Sticks with phenylethyl alcohol.


RESULTS
IIH patients (n=19) had significant impairment on both olfactory measures compared with matched controls (n=19). The olfactory threshold dilution levels were 9.07 (95% CI 1.85 to 5.81) and 3.83 (95% CI 7.04 to 11.10), p=0.001, and smell identification scores were 35.61 (95% CI 34.03 to 37.18) and 32.47 (95% CI 30.85 to 34.09), p=0.008, for control and IIH subjects, respectively. The threshold detection was mildly impaired in head-down tilt compared with upright position in the combined subjects (6.05 (95% CI 4.58 to 7.51) vs 6.85 (95% CI 5.43 to 8.27), p=0.004).


CONCLUSIONS
We demonstrated that IIH patients have marked impairment in olfactory threshold levels, out of proportion to smell identification impairment. There was also impairment in olfactory threshold in head-down tilt compared with upright positioning, but not for smell identification. The underlying mechanisms for olfactory threshold dysfunction in IIH patients need further exploration.
Department of Neurology, Baylor College of Medicine, Houston, Texas, USA.
Eric M
EM
Bershad
Department of Neurology, Baylor College of Medicine, Houston, Texas, USA.
Mian Z
MZ
Urfy
Department of Neurology, Baylor College of Medicine, Houston, Texas, USA.
Eusebia
E
Calvillo
Department of Optometry, University of Houston, Houston, Texas, USA.
Rosa
R
Tang
Department of Optometry, University of Houston, Houston, Texas, USA.
Christian
C
Cajavilca
Department of Neurology, Baylor College of Medicine, Houston, Texas, USA Departments of Ophthalmology, Neurology, and Neurosurgery, Houston Methodist and Weil Cornell, Houston, Texas, USA.
Andrew G
AG
Lee
Department of Neurology, Baylor College of Medicine, Houston, Texas, USA.
Chethan P
CP
Venkatasubba Rao
Department of Neurology, Baylor College of Medicine, Houston, Texas, USA.
Jose I
JI
Suarez
Department of Neurology, Baylor College of Medicine, Houston, Texas, USA.
Denise
D
Chen
D000328:Adult; D016022:Case-Control Studies; D005260:Female; D018475:Head-Down Tilt / Q000502:physiology; D006801:Humans; D008297:Male; D000857:Olfaction Disorders / Q000150:complications* / Q000503:physiopathology*; D011559:Pseudotumor Cerebri / Q000150:complications / Q000503:physiopathology*; D012684:Sensory Thresholds / Q000502:physiology; D055815:Young Adult
CSF Dynamics; Smell