C-IIH (Chronic IIH Imaging in Headache) study: Hospital-based pictorial review of Chronic IIH variants Neuroradiologist’s perspective

Meena Nedunchelian, Shriram Varadharajan

Neuroradiology, Kauvery Institute of Brain and Spine, Kauvery Hospital Radial Road, Chennai, Tamil Nadu, India

Introduction

Classical IIH Triad

Modified Dandy Criteria

  • Signs and symptoms of increased intracranial pressure
  • Absence of localizing findings on neurologic examination
  • Elevated CSF pressure, but with no cytologic or chemical abnormalities
  • Awake alert patient
  • No etiology for increased ICP on neuroimaging findings

Atypical IIH features

1). Prominent CSF/Arachnoid pits with multifocal areas of skull base attenuation – most common in middle cranial fossae

Clinical implication: They most likely represent CSF egress pathways in chronic raised ICP and often compensates pressure. Thus, these patients often are asymptomatic in the beginning and do not exhibit classical clinical or radiological IIH features.

2). Prominent enlarged Arachnoid Granulations (most commonly SSS and transverse venous sinuses) – follows CSF signal

Implications: They often mimic CVT like filling defects on MRV but can be differentiated by their CSF signals and central vein

3). Prominent skull base foramina – Meckel’s cave and posterior fossa

4) Brain herniation into Arachnoid Granulations (BHAG)

Clinical implications: Prominent skull base foramina and BHAG can be found in other conditions, and asymptomatic patients

CT Correlation

Bony windows on CT correlation shows scalloping of skull base with CSF attenuation areas corresponding to arachnoid pits

Clinical implications: Patients may present with non-traumatic/spontaneous CSF rhinorrhoeas or recurrent meningitis

Finally, Spine can also manifest CSF diseases: Atypical IIH features (case example)

IIH Presenting as Cervical Radiculopathy Due to Enlarged Perineural CSF Spaces

Clinical implications – IIH Patients may also present with neuropathic pain and radiculopathy, screening the spine may help

C-IIH (Chronic IIH Imaging in Headache) Study-Results

Hospital based study of prevalence of imaging findings in cohort of headache patients undergoing MRI in past year at tertiary center

Total patients260
Study duration1 year
Atypical IIH signs27%
Individual featuresPercentage (%)
Prominent CSF pits/ Arachnoid granulations54
Atretic cephalocele/ meningocele10
Brain herniation into arachnoid granulation9
Skull base attenuation13
Classical triad73

Nearly 1 in 4 patients with headaches had atypical imaging features on MRI that could suggest underlying chronic raised ICP/IIH variant which needs further evaluation for specific treatment

Limitations: Lack of clinical confirmation and CSF opening pressure in absence of LP.

Conclusion

Knowledge of atypical imaging manifestations of IIH is important in diagnosing chronic variants, especially in patients with headaches and other appropriate clinical contexts. IIH is an emerging epidemic, especially in the post-COVID era and neuroimaging needs to be at the forefront, conducting detailed and dedicated studies in future on IIH variants.

Tailored treatment strategies, including endovascular interventions can even be offered for refractory symptoms and intractable chronic headaches in this cohort of patients.

References

  • Toshniwal SS, Kinkar J, Chadha Y, Khurana K, Reddy H, Kadam A, Acharya S. Navigating the Enigma: A Comprehensive Review of Idiopathic Intracranial Hypertension. Cureus. 2024 Mar 16;16(3):e56256. doi: 10.7759/cureus.56256.
  • Wall M, Kupersmith MJ, Kieburtz KD, et al. The Idiopathic Intracranial Hypertension Treatment Trial: Clinical Profile at Baseline. JAMA Neurol. 2014;71(6):693–701. doi:10.1001/jamaneurol.2014.133.

Dr Meena Nedunchelian

Dr. Meena Nedunchelian
Junior Consultant – Radiology

Dr. Shriram Varadharajan - Best Neuroradiologist in Chennai

Dr. Shriram Varadharajan
Senior Consultant- Neuroradiology

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