Idiopathic intracranial hypertension – is it really idiopathic?

11th December 2025, A/Prof Chee L Khoo

We all have a handful of patients witth idiopathic intracranial hypertension. It is often diagnosed by someone else incidentally. While the full pathophysiology of the condition is still not clear, we know enough about the condition to know who may be at highest risk and perhaps, diagnose the condition early to prevent visual loss. Medical treatment is possible in the early stages and cerebrospinal fluid (CSF) shunting is no longer the only surgical options. Headaches is the most common initial symptom but we see so many patients with headaches that we don’t find a cause for. Who may have IIH? Which patients with headaches should we be on the lookout for IIH? 

Max Nonne, a German neurologist, described a syndrome of headache accompanied by swollen optic disks in patients with CSF pressure back in 1904 (1). He called the condition “pseudotumor cerebri,” because it behaves like a tumour but none of these patients have a tumour. He described a clinical syndrome of chronically elevated intracranial pressure of unknown aetiology. As diagnostic options grew broader and more effective over time, however, numerous pathological conditions that can cause chronically high intracranial pressure were identified, which occasioned its classification into a primary and secondary form.  

The prevalence of IIH is 8.6 cases per 100 000 in the general population (2,3). Overwhelmingly, 95% of sufferers are overweight or obese women of reproductive age. It occurs in 1:500 women whose BMI is > 30 kg/m2 (4). As obesity rates are rising, we can expect increasing numbers of IIH arriving at our doorstep. A history of recent significant weight gain often precedes the onset of symptoms although obviously, the raised CSF has been present and increasing for some time. There are children who suffers from IIH but the big gender difference is not seen in this group and overweight in this group is not as common as in adults (5-7). 

Pathophysiology? 

They used to think that IIH is caused from an overproduction of CSF but that has been largely refuted. Because most of the sufferers are obese, perhaps, high intra-abdominal and intrathoracic pressure increases cerebral venous pressure and reduces the absorption of CSF, ultimately causing intracranial pressure to rise. Why the gender difference? If anything, women tend to accumulate fat around the waist than in the abdomen. What about children who are not obese? 

There is some speculation in the role of various hormonal factors in the pathophysiology. Leptin resistance is associated with obesity. In IIH patients, the serum leptin concentration is significantly higher than in obese control subjects, pointing the discussion to central leptin resistance (8,9). Interestingly, leptin concentration in the affected patients is higher in women than in men, and hence this mechanism might explain why women are particularly affected by IIH. The role of androgens and cortisol has also been cited as possible culprits. 

Another interesting but confusing pathology is transverse sinus stenosis (TSS).  TSS has been identified in ~ 90% of adult IIH patients, and in cases of bilateral TSS, endovascular treatment of the stenoses may alleviate or eliminate IIH 10-12). Haemodynamically, we need bilateral TSS to affect CSF absorption. Further, it is not known whether TSS is the primary effect causing IIH or the other way round. Is TSS the result from IIH or is IIH caused by TSS? 

Symptoms 

The current diagnostic criteria from Friedman et al. are based on a modified version of the Dandy criteria (13): 

Papilloedema;  

Unremarkable neurological examination except for cranial nerve disorders (especially 6th cranial nerve palsy);  

MRI without structural lesions, signs of hydrocephalus or meningeal enhancement; Physiological CSF composition; and opening pressure of ≥25 cm CSF in adults and ≥ 8 cm CSF in children (in non-sedated children of normal weight ≥25 cm) are required for the diagnosis of IIH.  

The clinical presentation of IIH-associated headache is extremely variable, which is why the clinical characteristics of headache were removed from the diagnostic criteria. It is often described as bilateral frontal or retroorbital. It is often reported to be worse with coughing or straining, However, all these can be present in patients with migraine, chronic sinusitis or tension headaches and thus, often diagnosis is delayed.  

Other symptoms include: 

  • Visual disorders (from papiloedema) 
  • Cranial nerve palsies 
  • Olfactory dysfunction 
  • Tinnitus 
  • Cognitive impairment 

MRI changes 

The most significant IIH-associated changes in a cerebral MRI include: 

  • An empty sella,  
  • Flattened posterior aspect of the optic globe 
  • Distended perioptic subarachnoid space with or without a tortuous optic nerve 
  • The presence of uni- or bilaterally localized TSS  

Management 

Naturally, treatment options depends on the severity of elevated CSF pressure (causing headaches) and the state of the optic nerve. The principal aims of IIH treatment are the preservation of visual acuity and the relief of headache.  

Weight loss 

Since IIH is very related to obesity, weight loss has to be a major component of the multimodal management. Weight loss significantly reduces intracranial pressure, papilledema, the associated visual disturbances and headache. Even small changes can have a major influence on the course of the disease. Regaining of weight is associated with an increased recurrence of IIH. 

Lumbar puncture 

Often, lumbar puncture is part of the diagnostic workup. It is thought that relieving the CSF pressure re-establish some form of CSF production-absorption equilibrium and thus, improve TSS. The brief improvement of CSF pressure can relieve the headaches for weeks.  

Pharmacotherapy 

Acetazolamide (up to 4000mg per day) have been demonstrated to improve papilledema, visual deficits, and headache (14). Othe agents used include topiramate in those not tolerant of acetazolamide, frusemide and octreotide (which is used to inhibit growth hormone) although efficacy data is not robust. Topiramate, incidentally, helps with weight loss. 

Surgical interventions 

Ventriculoperitoneal or a lumbo-peritoneal shunt is what is frequently performed to improve the CSF drainage although data on long-term efficacy and safety are sparse(15). Shunts generally improves vision but not necessarily, the headaches.  

Endovascular stents can eliminate the TSS improves venous drainage, which in turn increases CSF absorption, ultimately reducing CSF pressure (16). Long term efficacy and safety data is still lacking. 

Fenestration of the optic nerve sheath consists of an incision in the meninges surrounding the optical nerve. It is thought that this reduces the CSF pressure around the optic nerve. Although theoretically, the fenestration is repaired by the meninges very quickly, the symptom relief persist for some time. This intervention should therefore be considered only in particular treatment-resistant cases where the risk of irreversible vision loss is high (17). 

In summary, IIH may not be common (at the moment) but is expected to increase as the rates of obesity increases. Early diagnosis is important to reduce the need for more invasive management options. Headaches is a common presenting initial symptom but we see lots of headaches in primary care and many of the headaches like migraines, tension headaches or chronic sinusitis are diagnoses of exclusion and often not confirmed by further investigations. Most sufferers are women of reproductive age who are obese. It is important to have a high index of suspicion in this group of patients presenting with unrelenting headaches. 

References: 

References: 

  1. NonneM.“U ̈ ber falle vom symptomkomplex “tumor cerebri” mit ausgang in heilung (pseudotumor cerebri). Dtsch Z Nervenheilkd 1904;27:169–216
  2. Durcan FJ, Corbett JJ, Wall M. The incidence of pseudotumor cerebri. Population studies in Iowa and Louisiana. Arch Neurol 1988; 45: 875-877
  3. Radhakrishnan K, Ahlskog JE, Cross SA. et al. Idiopathic intracranial hypertension (pseudotumor cerebri). Descriptive epidemiology in Rochester, Minn, 1976 to 1990. Arch Neurol 1993; 50: 78-80
  4. Wall M. Idiopathic intracranial hypertension. Neurol Clin 2010; 28: 593-617
  5. Ko MW, Liu GT. Pediatric idiopathic intracranial hypertension (pseudotumor cerebri). Horm Res Paediatr 2010; 74: 381-389
  6. Cinciripini GS, Donahue S, Borchert MS. Idiopathic intracranial hypertension in prepubertal pediatric patients: Characteristics, treatment, and outcome. Am J Ophthalmol 1999; 127: 178-18
  7. Sheldon CA, Paley GL, Xiao R. et al. Pediatric idiopathic intracranial hypertension: Age, gender, and anthropometric features at diagnosis in a large, retrospective, multisite cohort. Ophthalmology 2016; 123: 2424-2431
  8. Ball AK, Sinclair AJ, Curnow SJ. et al. Elevated cerebrospinal fluid (CSF) leptin in idiopathic intracranial hypertension (IIH): Evidence for hypothalamic leptin resistance?. Clin Endocrinol (Oxf) 2017; 37: 113-121
  9. Lampl Y, Eshel Y, Kessler A. et al. Serum leptin level in women with idiopathic intracranial hypertension. J Neurol Neurosurg Psychiatry 2002; 72: 642-643
  10. Dinkin MJ, Patsalides A. Venous sinus stenting in idiopathic intracranial hypertension: Results of a prospective trial. J Neuroophthalmol 2017; 37: 113-121
  11. Farb RI, Vanek I, Scott JN. et al. Idiopathic intracranial hypertension: the prevalence and morphology of sinovenous stenosis. Neurology 2003; 60: 1418-1424
  12. Ahmed RM, Wilkinson M, Parker GD. et al. Transverse sinus stenting for idiopathic intracranial hypertension: a review of 52 patients and of model predictions. AJNR Am J Neuroradiol 2011; 32: 1408-1414
  13. Friedman DI, Liu GT, Digre KB. Revised diagnostic criteria for the pseudotumor cerebri syndrome in adults and children. Neurology 2013; 81: 1159-1165
  14. Wall M, McDermott MP, Kieburtz KD. et al. Effect of acetazolamide on visual function in patients with idiopathic intracranial hypertension and mild visual loss: The idiopathic intracranial hypertension treatment trial. JAMA 2014; 311: 1641-1651
  15. Sinclair AJ, Kuruvath S, Sen D. et al. Is cerebrospinal fluid shunting in idiopathic intracranial hypertension worthwhile? A 10-year review. Cephalalgia 2011; 31: 1627-1633
  16. Owler BK, Parker G, Halmagyi GM. et al. Cranial venous outflow obstruction and pseudotumor Cerebri syndrome. Adv Tech Stand Neurosurg 2005; 30: 107-174
  17. Hoffmann J. Headache Attributed to Intracranial Hypertension and Hypotension. In: Mitsikostas DD, Pameleire K. Hrsg Pharmacological Management of Headaches. 1. Aufl. Springer ; 2015: 189-205