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Editorial

Intracranial hypertension, headacheand obesity: Insights from magneticresonance venography

Deborah l Friedman

Idiopathic intracranial hypertension without papilloe-

dema (IIHWOP) is uncommon, accounting for, at

most, 5% of patients with IIH evaluated by neuro-

ophthalmologists (1). In contrast to patients with IIH

and papilloedema, patients with IIHWOP are less

obese, have lower cerebrospinal fluid pressures, and

are more likely to have non-organic visual loss (1).

This entity is perhaps more readily diagnosed among

headache specialists than neuro-ophthalmologists and

is suspected in obese women with intractable or chronic

daily headaches (2).

The integral relationship between the central venous

system and intracranial pressure has been emphasised

over the past several years with the discovery of venous

sinus abnormalities in patients with IIH (3). Morpho-

logical irregularities and abnormal pressure gradients

within the transverse sinuses are well described. In

most cases, transverse venous sinus stenosis appearsto be a result of high intracranial pressure rather than

its cause (4). The transverse sinuses are asymmetric in

most individuals and a unilateral hypoplastic sinus is

considered a normal variant. However, bilateral trans-

verse sinus stenosis (BTSS) may be associated with

intracranial hypertension.

In this issue of Cephalalgia, Bono and colleagues

studied 98 patients with chronic migraine and chronic

tension type headache using magnetic resonance venog-

raphy and 1-h continuous lumbar CSF pressure moni-

toring (5). Their findings are notable in several respects.

Strikingly, their patients were obese, regardless of

CSF pressure status. Patients with normal CSF pres-

sure (Group 1) were less overweight than in the groups

with either intermittently (Group 2) or consistently

(Group 3) elevated CSF pressure, and some patients

in Group 1 had a normal body mass index (BMI),

but overall this cohort was overweight. There was no

different in BMI between subjects in Groups 2 and 3.

Obesity is a risk factor for both IIH and the develop-

ment of chronic daily headache (6).

Although there was a statistically significant differ-

ence in both mean CSF pressure and opening pressure

between the three groups, only some of the patients in

Group 3 met criteria for the diagnosis of IIH by current

standards (7). Pressures between 201249 mm CSF are

non-diagnostic (8).

BTSS has been noted in a majority of patients with

IIH by various investigators. It is less commonly

encountered in a typical practice setting, even in

patients with papilloedema. The high prevalence of

BTSS in this cohort is perhaps attributable to the imag-

ing technique used, which the investigators previously

found to have a very high detection rate of transverse

sinus stenosis (three dimensional phase contrast images

with 15 cm/s velocity encoding). Conventional MR

venography is often performed using two dimensional

time of flight, and the images are likely subjected to less

scrutiny in the practice setting than the research setting.

All subjects in Groups 2 and 3 had BTSS, whereas only

four of 54 patients in group 1 had BTSS. As previouslynoted, unilateral transverse sinus stenosis was not asso-

ciated with abnormal intracranial pressure.

One-hour monitoring showed mean pressures that

were consistently higher than the opening pressure in

all groups. The importance of this finding cannot be

overemphasised. An isolated CSF pressure measure-

ment is but a snapshot in time and may be spuriously

high or low, depending on the situation and technique

employed. Prolonged monitoring also revealed B-waves

in Groups 2 and 3; B-waves are frequently recorded

with increased intracranial pressure of various aetiolo-

gies, although there is far greater experience defining

pressure wave abnormalities with intracranial pressure

monitoring systems than with lumbar recording

methods.

Digre and colleagues (1) found that treatment of

patients with IIHWOP with agents conventionally

University of Rochester, USA.

Corresponding author:

Dr Deborah l Friedman. University of Rochester, New York, USA

Email: deborah_friedman@urmc.rochester.edu

Cephalalgia

30(12) 14151416

! International Headache Society 2010

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DOI: 10.1177/0333102410370872

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used for IIH was less than satisfactory than in patients

having IIH with papilloedema, and shunting was not

always beneficial. The patients of Bono et al. were trea-

ted with a low dose of acetazolamide and topiramate

which improved the headache in most subjects.

However, the response to acetazolamide and topira-

mate is not specific, as both medications have a symp-tomatic effect on headache. Interestingly, some of the

patients had been previously treated with topiramate

for headaches without improvement (personal commu-

nication with Professor Bono); it is a bit surprising that

adding a relatively low dose of acetazolamide would

dramatically increase their therapeutic response.

These patients were not re-imaged after treatment; par-

adoxically, another study by these investigators showed

that the BTSS persisted in IIH patients who were suc-

cessfully treated with medications rendering them

asymptomatic with normal CSF pressures (9). These

findings contrast with other reports demonstrating

reversal of venous sinus stenosis acutely after measures

to lower CSF pressure (4,10).

In summary, this paper raises intriguing questions

about the pathophysiology of IIH, the contribution of

both obesity and intracranial pressure to chronic head-

aches, and the possibility of a continuum of chronic

daily headache to IIH. It underscores the involvement

of the cerebral venous sinuses in the hydrodynamics of

CSF pressure. BTSS may be a marker of increased

intracranial pressure but it is not a consistent finding

in patients with IIH and papilloedema in clinical prac-

tice. Whether BTSS is the cause or the effect of intra-

cranial hypertension, its detection by magneticresonance venography in patients with chronic head-

aches may provide important information into the

nature of their headache disorder and subsequent man-

agement. Lumbar puncture, currently the gold

standard for diagnosing IIH and other disorders affect-

ing intracranial pressure, may demonstrate misleading

results at times but it is widely available and more

practical than prolonged monitoring in the clinical set-

ting. A high opening CSF pressure in and of itself is

neither specific nor diagnostic and must to be used in

context with other data from the history, examination,

neuroimaging and laboratory to arrive at the correct

diagnosis.

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