Adult idiopathic intracranial hypertension

Evolving evidence in adult idiopathic intracranial hypertension: pathophysiology and management — Mollan et al. — Journal of Neurology, Neurosurgery & Psychiatry — February 2016

Idiopathic intracranial hypertension (IIH) is a rare but important disease associated with significant morbidity.

The pathophysiology of IIH is incompletely characterised; suggested underpinning mechanisms include the role of cerebrospinal fluid regulation as well as metabolic and endocrinological perspectives

This review will provide an up-to-date discussion on the potential pathogenic mechanisms and management of IIH.  

Pathophysiology

The underlying pathogenesis of IIH is uncertain. Raised ICP is a uniform characteristic, but the mechanism by which ICP is elevated in IIH is not clear.

It is also questionable whether a single unifying mechanism elevates ICP in these individuals (figure 1). Secondary causative factors which lead to elevation of ICP may be mechanistically distinct from truly idiopathic causes.

pathogenesis of IIH

Figure 1: Schematic diagram of the possible pathophysiological mechanisms in idiopathic intracranial hypertension (IIH).

Cerebrospinal fluid (CSF) is produced mainly by the choroid plexus epithelial cells, with a small amount being secreted by ependymal cells that line the ventricular system.

Classically, CSF was thought to drain predominantly through the subarachnoid space through arachnoid granulations into the superior sagittal sinus.

Evidence also suggests CSF drains through the cribriform plate along cranial nerves into the nasal lymphatics (yellow).

The most recent hypothesis proposes bulk flow of fluid along perivascular routes (glymphatic pathway) which is cleared from the brain into the subarachnoid CSF, bloodstream or cervical lymphatics. Supporting this concept is the recent discovery of lymphatic vessels (yellow) in the dura that drain into the deep cervical lymph nodes.

Role of altered CSF dynamics

Changes in the volume of blood, CSF and brain tissue influence ICP. IIH likely represents a disorder of CSF regulation, potentially through CSF hypersecretion or reduced drainage.

  • Increased CSF production
  • Reduced CSF drainage
  • Role of obesity
  • Role of gender

Anatomical influence

Improvements in brain venography imaging reveal that most patients with IIH have anatomical abnormalities of the cerebral venous sinus system

These include stenosis of the dominant (figure 2) or both transverse sinuses. There are two recognised morphological types of venous stenosis, and a combination of both can occur in one patient

Reducing ICP has led to resolution of stenosis in some patients, suggesting that the stenoses are a result of raised ICP externally deforming the venous sinuses, and not a primarily cause

Additionally, elevated venous sinus pressure in the setting of venous sinus stenosis, may impair CSF drainage at the arachnoid granulation tissue further exacerbating a cycle of intracranial hypertension

Clinical features

Diagnostic criteria

Table 1 Diagnostic criteria for idiopathic intracranial hypertension (IIH) adapted from Friedman et al1

Diag Criteria for IIH

Additionally, they have recognised that IIH may occur in the absence of symptoms of elevated ICP and rarely in the absence of papilloedema, so-called IIH without papilloedema (IIHWOP).

There are a number of identifiable causes that give rise to secondary intracranial hypertension such as anaemia, obstruction to venous drainage and exposure to various pharmacological agents, for example, tetracyclines, hypervitaminosis vitamin A and retinoids (table 2). Neuroimaging, either MRI or CT or MRI, must exclude hydrocephalus, structural lesions, abnormal meningeal enhancement and cerebral venous sinus thrombosis.

Pharmacological agents Systemic conditions
Antibiotics: tetracycline and derivatives, vitamin A derivatives: isotretinoin, all-trans-retinoic acid (for acute promyelocytic leukaemia)
Hormonal agents: corticosteroid withdrawal, growth hormone, thyroxine replacement in children
Other agents: lithium, nalidixic acid, rofecoib, cimetidine
Haematological: anaemia
Respiratory: obstructive sleep apnoea
Renal: renal failure
Endocrine: obesity, weight gain, polycystic ovarian syndrome, Cushing’s disease, Addison’s disease, hypoparathyroidism
Genetic: turner syndrome
Autoimmune: systemic lupus erythematosus
Nutritional: hypervitaminosis A
Venous: cerebral venous sinus thrombosis, superior vena cava obstruction, increased right-sided heart pressure

Table 2 Conditions that may cause intracranial hypertension

Comorbidities

Polycystic ovarian syndrome (PCOS) is a chronic endocrine condition characterised by menstrual irregularities, ovarian dysfunction, hyperandrogenism and hirsutism. The prevalence of PCOS in women with IIH is reported to be as high as 39–57%,46 compared to 7–18% in the general population.

Assessment and investigations

Management

The 2015 Cochrane review concluded that there is no current consensus on the best management strategy for IIH.12 The two key approaches in IIH are to preserve visual function, and to reduce long-term headache disability. The treatments employed depend largely on the patient’s level of visual function and rate of progression. Accepted medical interventions range from dietary therapy (eg, responsible and sustainable weight loss, lifestyle modification, low-salt diet) to medications and surgical treatment.

Treatment of headache

Headache is the most common presenting feature in IIH and leads to significant morbidity

Many patients do not have the classical headache phenotype attributed to raised ICP and the International Classification of Headache Disorders, which does not specify a particular headache phenotype (ICHD 3) has poor specificity (53%) in IIH.

Many patients with IIH have daily headache (86%) that often resembles migraine or tension-type headache.

IIH headache improves post-LP in 72%, but an improvement also occurs in 25% of those with headache without IIH or a pressure syndrome.

Headaches outcomes are poor even in those with no prior history of headache, with 57% having headaches at 12 months

Accurate headache phenotyping is key, and mixed headache types frequently coexist (high pressure, migraine, tension-type, low pressure in those with a shunt). Medication overuse headaches often occur and are underdiagnosed.

Our practice is to treat the predominant headache phenotype, typically using migraine-preventative strategies

It is worthy of note that some of the commonest medications here can cause weight gain.

Health-related quality of life

For patients with IIH, the journey is typically extremely challenging

The diagnostic process with urgent brain imaging and LP is frightening and painful

For many, the reality is a long-term illness dominated by drug side effects, headaches, potential depression and in some surgery, which can be recurrent. The impact on their family life, occupation and earning potential is great.

Studies verify that IIH has a significant effect on health-related quality of life (QOL) patients with IIH have also been found to have higher levels of anxiety, depression and fatigue than controls

Cognition

A number of factors could impact on cognitive function in IIH (depression, headaches, sleep apnoea, obesity, medications and raised ICP)

One study reported reduced reaction time and processing speed in patients with acute IIH

Another cross-sectional study has also demonstrated multidomain mild cognitive impairment in IIH, with lowest scores in visuospatial, attention and global indices

Cognitive dysfunction may contribute to the patient morbidity, however, it is largely uncertain whether the deficits are chronic or related to treatment effects.

IIH without papilloedema

In patients with chronic daily headache, raised CSF pressure has been identified in some patients, particularly in the obese, despite the lack of papilloedema.

Isolated, single LP measures are not ideal in assessing patients with chronic headaches as ICP fluctuates diurnally. In some cases, a period of prolonged CSF monitoring, ideally while the patient is ambulatory is helpful

As patients with IIHWOP do not have papilloedema and do not develop papilloedema, they do not develop visual loss

Conclusion

For clinicians managing patients with IIH, questions remain about the optimal evidence-based approach for management

IIH is a multisystem disorder encompassing neuroscience, ophthalmology and endocrinology and cross-specialty collaboration will be integral to advance our understanding of IIH. In the clinical environment, multidisciplinary input is essential to optimise patient care

3 thoughts on “Adult idiopathic intracranial hypertension

  1. abodyofhope

    I’ve been tested many times for IIH, as I’m symptomatic for Pseudo tumor Ceribri, and it’s a terrible condition to live with. Many go blind slowly over their lives, and have to have regular spinal taps to manage the intense head pain, swelling of the face, vomiting, leaky eyes, ears, nose, and brain pressure. Others have brain surgery, which, as stated, is more often recurrent than a single surgery. This condition causes so many with IIH cognitive disruption which is closer to dementia than brain fog, vertigo, neurological pain, can cause seizures, and the head pain is always the most severe of anything else.
    Researchers tend to minimize the symptoms and effects of an illness, but this one is like dying of a brain tumor over an entire life. My heart goes out to anyone living with IH or IIH. Thank you for sharing and for raising awareness.

    Liked by 1 person

    Reply
  2. Jan Groh

    I can’t help wondering what role Mast Cell Activation Disease (MCAD – the umbrella term for all forms including Masto and MCAS) plays in some of these cases, which I find commonly comorbid in EDS patients. I’ll tell you this much, my CSF pressure (or intracranial pressure) goes way up during my MCAS reactions. Worst headaches I’ve ever had, make me seriously almost reach for an ice pick to pop my head and relieve the pressure. (Thankfully better managed now with quercetin, diet and other meds.) But along with just neurology (shape of your ventricles, drain pipes, etc.) and CCI and settling, I can’t help wondering about the above, but never see any mention of it outside of Dr. Diana Driscoll’s Theory. (See prettyill.com for that.)

    Liked by 1 person

    Reply
    1. Zyp Czyk Post author

      I don’t believe I have mast cell issues, but I do get headaches that have symptoms of intracranial hypertension, like being worse when I lie down or put any pressure on my head.

      I don’t have an ice pick, but i discovered that a few hard whacks of my head against the solid wood backdoor actually give me a few minutes of relief as my body tries to sort out all the different pain signals coming from my head.

      The pain of hitting my head is a welcome change from the unrelenting headache pain :-)

      Like

      Reply

Other thoughts?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.