Assessment of the Olfactory Function in Patients With Idiopathic Intracranial Hypertension Using the Sniffin' Sticks Test: A Case-Control Study

Evaluation of peripheral and central olfactory regions by MRI in patients with idiopathic intracranial hypertension

OBJECTIVES

We investigated the peripheral and central smell regions in patients with idiopathic intracranial hypertension (IIH) by cranial MRI.

METHODS

In this retrospective study, cranial MRI images of 43 adult patients with IIH (Group 1) and 43 healthy adults without IIH (Group 2) were included. In both groups, peripheral [Olfactory bulb (OB) volume and Olfactory sulcus (OS) depth] and central smell regions (insular gyrus and corpus amygdala area, and thalamus volume) were measured in cranial MRI.

RESULTS

Bilateral OB volume and insular gyrus area, and right corpus amygdala and thalamus volumes of the IIH group were significantly lower than those of the control group (p < 0.05). In the IIH group, OB volume of the right side was significantly lower, and insular gyrus area of the right side was significantly higher than those of the left side (p < 0.05). In the IIH group, there were positive correlations between OB volumes; OS depths; insular gyrus areas; corpus amygdala areas; and thalamus volumes bilaterally (p < 0.05). In older patients, right OS depth and right corpus amygdala area decreased (p < 0.05).

CONCLUSION

In conclusion, IIH may be related to olfactory impairment. Cranial MRI images showed a decrease in peripheral (OB volume) and central (insular gyrus and corpus amygdala area and thalamus volume) smell regions. To prevent olfactory impairment in IIH patients, treatment should be done in IIH patients to decrease intracranial pressure. It is very important to prevent the circulation of CSF with increased pressure between the sheets of the olfactory nerve in IIH patients.

Atypical presentations of idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) is a disorder of unknown etiology that results in isolated raised intracranial pressure. Classic symptoms and signs of IIH include headache, papilledema, diplopia from sixth nerve palsy and divergence insufficiency, and pulsatile tinnitus. Atypical presentations include: (1) highly asymmetric or even unilateral papilledema, and IIH without papilledema; (2) ocular motor disturbances from third nerve palsy, fourth nerve palsy, internuclear ophthalmoplegia, diffuse ophthalmoplegia, and skew deviation; (3) olfactory dysfunction; (4) trigeminal nerve dysfunction; (5) facial nerve dysfunction; (6) hearing loss and vestibular dysfunction; (7) lower cranial nerve dysfunction including deviated uvula, torticollis, and tongue weakness; (8) spontaneous skull base cerebrospinal fluid leak; and (9) seizures. Although atypical findings should raise a red flag and prompt further investigation for an alternative etiology, clinicians should be familiar with these unusual presentations.

Association of pediatric idiopathic intracranial hypertension with olfactory performance

OBJECTIVE

To assess the association between pediatric Idiopathic intracranial hypertension (IIH) and olfactory performance.

METHODS

A cross-sectional comparative study was conducted including 17 patients under 18 years diagnosed with IIH at a tertiary hospital and 17 healthy age- and sex-matched subjects. All participants underwent the semi-objective chemosensory Sniffin' Sticks test for evaluation of odor threshold (OT), indicative of peripheral olfactory function, and odor identification (OI), reflecting higher cognitive olfactory processing. Scores were compared and referred to the updated normative values. Demographic, clinical, and neuroimaging data were collected from the medical files. The patients with IIH were reassessed for olfactory function and clinical state at the subsequent follow-up, under treatment.

RESULTS

Compared to controls, the IIH group had a significantly lower mean OT score (6.41 ± 3.43 vs 10.21 ± 2.79, p = 0.001) and higher rate of OT score below the 10th percentile for age and sex according to the normative values (47.1% vs 0%, p = 0.001). There was no significant between-group difference in mean OI scores (9.82 ± 1.63, vs 10.59 ± 1.84, p = 0.290). OT scores were not associated with sex, age, body mass index, neuroimaging abnormalities, or lumbar puncture opening pressure. At the follow-up assessment, the OT scores were improved (9.36 ± 4.17 vs 6.7 ± 3.32, p = 0.027) whereas the OI scores were unchanged (9.88 ± 2.5 vs 9.69 ± 1.58, p = 0.432).

CONCLUSIONS

As reported in adults, children and adolescents with IIH appear to have a selective reversible deficit in olfactory detection threshold, which may imply a reduction in peripheral olfactory perceptual ability. Future studies should examine the predictive value of olfactory function for IIH.

An update on idiopathic intracranial hypertension in adults: a look at pathophysiology, diagnostic approach and management

Idiopathic intracranial hypertension is a neurological syndrome determined by a rise in intracranial pressure without a detectable cause. Course and prognosis may be changeable, requiring a multidisciplinary approach for its diagnosis and management. Although its precise pathogenesis is still unknown, many studies have been carried out to define the possible causal and associated factors, such as retinoids, steroid hormones, body mass index and recent weight gains, cytokines and adipokines levels. The clinical presentation can be variable including chronic headache, disturbance of vision, diplopia and tinnitus. Even if papilloedema is considered the most specific sign, it could not be observed in more than 5% of patients during the evaluation of the fundus oculi. Neuroradiological signs acquire greater importance in patients who do not present papilloedema and may suggest the diagnosis of idiopathic intracranial hypertension. Other assessments can be useful in the diagnostic process, such as optical coherence tomography, visual evoked potentials, ocular ultrasonography and fundus fluorescein angiography and autofluorescence. Nonetheless, cerebrospinal fluid pressure measurement is required to establish a definite diagnosis. Management may be different, since surgical procedures or lumbar punctures are often required when symptoms develop rapidly leading to a loss of visual function. Apart from these cases, patients can be treated with a pharmacological approach and low-calorie diet, but they also need to be monitored over time since relapses years later are not uncommon.