Clinicoradiological profile of idiopathic intracranial hypertension

INTRODUCTION

Idiopathic intracranial hypertension (IIH) is characterized by an increase in intracranial pressure (ICP) without any identifiable etiology.^[1,2] IIH is a rare disease, affecting 4.69/100,000 in the general population and the incidence of IIH is increasing with the increasing incidence of obesity.^[3,4] The incidence of IIH is 20/100,000 in the obese population, with up to 64/100,000 in females.^[5] IIH which was previously known as benign intracranial hypertension, is now classified under the umbrella term of pseudotumor cerebri syndrome with classification into primary or secondary depending on the presence or absence of any identifiable etiology.^[6] According to the International Classification of Headache Disorders-3, IIH is described as a new-onset headache or significant worsening of a preexisting headache accompanied by clinical symptoms/signs, and/ or neuroimaging signs of raised increased ICP.^[7] The majority of IIH patients are phenotypically obese females of reproductive age group where headache is the primary comorbidity.^[1]

MATERIAL AND METHODS

This is a retrospective study, done at a super-specialty neuroclinic, in West Bengal, from July 2021 to June 2022. All the patients were examined by a single neurologist on an outpatient basis. Patients were enrolled in the study after proper consent.

RESULTS

The most common clinical presentations were headache and transient visual obscurations (TVOs) followed by painless loss of vision, visual field (VF) changes and double vision. We found that 7 out of 12 cases were presented with headache (58.3%) out of which only 3were migrainous and the rest were non-migrainous. TVOs was presenting complaints of 7 patients (58.3%) with or without headache, 3 of them had no headache. Painless visual loss was there in 3 patients (25%), out of which only one case was bilateral (33%).

In all cases, MRI was suggestive of IIH with findings such as empty sella sign, dilated, and tortuous optic nerve. Transverse sinus stenosis in 3 cases and scleral flattening in 1 case were seen, respectively. On fundoscopy, papilledema was there in 4 cases where as one case had unilateral optic atrophy. The average cerebrospinal fluid (CSF) opening pressure was 31.25 cm of water. Two-fifth of cases were obese.

The most common age group of patients of IIH was 31–40 years [Table 1].

DISCUSSION

IIH, also known as primary pseudotumor cerebri, is characterized by increased ICP without any intracranial or spinal cord mass lesions and with normal-sized ventricles, normal CSF concentrations of protein and glucose, no cells in the CSF, and papilledema (Friedman et al., 2013^[8,9] and modified Dandy criteria, 1985^[10]).

IIH Diagnostic criteria; Friedman et al. 2013

1. Papilledema

2. Normal neurological examination (except sixth cranial nerve palsy)

3. Neuroimaging: normal brain parenchyma (no hydrocephalus, mass, structural lesion, or meningeal enhancement). Venous thrombosis was excluded in all

4. Normal CSF constituents

5. Elevated lumbar puncture pressure >25 cm CSF.

IIH was originally considered a benign syndrome of increased ICP with unremarkable imaging findings.^[8,11] Over decades of research, it has been well understood that IIH is associated with characteristic imaging findings and has the potential of causing significant visual morbidity.^[12,13] MRI is considered the gold standard investigation to exclude secondary causes of elevated ICP such as intracranial mass lesions, venous sinus thrombosis, and subarachnoid hemorrhage and to identify structural alterations associated with IIH such as empty sella turcica, flattening of the posterior optic globe, enlargement of the optic nerve sheath, and an increased tortuosity of the optic nerve.^[14-18]

Over 90% of patients diagnosed with IIH experience headaches. Headache is the most common cause of morbidity and disability after the visual components of the disease are resolved.^[3,19] The headache phenotype in IIH is predominantly migrainous, thus leading to a condition mimicking chronic migraine [Figures 1 and 2].^[20] In addition to headache, clinical symptoms are mainly visual disturbances such as TVOs, VF loss and binocular diplopia – due to cranial nerve VI palsy and pulsatile tinnitus, back, and neck pain.^[8,21] Most common VF defects are due to enlarged blind spots followed by loss of inferonasal portion of the VF.^[6,22] Papilledema and raised ICP should be considered as the most severe stage of the spectrum whereas headache and pulsatile tinnitus could be considered as a benign form of IIH.^[23] IIH is fulminant if the decline in visual function occurs abruptly within 4 weeks of diagnosis of IIH. IIH is said to be typical in the female of childbearing age with BMI >30 kg/m² whereas in male and non-obese cases, more investigations are required to rule out secondary causes; hence described as atypical IIH.^[24]

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Figure 1:

Visual symptoms in the study population.

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Figure 2:

Headache pattern and visual symptoms in patients with IIH

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In our study, headache was presenting complaints in 58% of the cases whereas visual symptoms were present in 91% of cases out of which TVO was most common seen in 58% of cases. Loss of vision was there in 25% of cases and double vision was symptom in only 8% of the total case [Table 2]. According to the idiopathic intracranial hypertension treatment trial (IIHTT), headache was the most common symptom (84%), TVOs occurred in 68% of patients, diplopia in 22%, and pulse synchronous tinnitus in 52%. Only 32% reported visual loss.^[25] In IIHTT, for CSF opening pressure of 200–250 mm water at least one of the following is required for diagnosis –pulse synchronous tinnitus, VI^th nerve palsy, Frisen Grade II papilledema, echography for drusen negative and no other disc anomalies mimicking disc edema present, magnetic resonance venography with lateral sinus collapse/ stenosis preferably using auto-triggered elliptic centric-ordered technique, partially empty sella on coronal or sagittal views and optic nerve sheaths with filled out CSF spaces next to the globe on T2-weighted axial scans.^[25]

Less than half, that is, 42% of cases were obese [Figure 3]. All patients (100%) were female. In large studies, <10% of patients are male, for example, in IIHTT, only 2.4% were male.^[25,26] In our study, the average CSF opening pressure was 31.25 cm of water [Table 3]. Only 1case (8.33%) was drug induced (levofloxacin).

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Figure 3:

Obese and Non-obese patients with IIH.

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In our study, MRI findings such as empty sella, optic nerve tortuosity, and globe flattening were found in 100%, 100%, and 8% cases, respectively. The previous study by Agid et al. shows optic nerve tortuosity to be present in 40% of people with IIH and 8.9% of controls.^[27,28] Agid et al. found empty sella to be present in 26.7% of people with IIH and 5.4% of controls whereas globe flattening was present in 43.3% of people with IIH and 0% of controls.^[17,27] Absence of MRI findings does not rule out IIH.^[27]

CONCLUSION

IIH is most prevalent in females of age group 31–40 years. Headache (58.3%) and/or TVOs (58.3%) are the most common presentation of IIH in our study. Clinical suspicion is of utmost importance for diagnosis of IIH to prevent complications. Every patient with headache and visual symptoms should undergo an MRI brain scan.