A woman in her early thirties came to my office last spring carrying a printed spreadsheet of her headaches — fourteen months of them, almost every day. Three neurologists, two preventives, one MRI reported as normal. On her way out, coat already half on, she mentioned almost as an afterthought that she could hear her own pulse in her left ear, like a seashell held against it, and that a few times a week her vision went grey for about ten seconds when she stood up from the couch. Nobody had written either of those down. Within a week she had a diagnosis that was not migraine, and treatment aimed at protecting her eyesight.
If you have daily or near-daily headache together with a rhythmic whooshing in one or both ears that keeps time with your heartbeat, and brief seconds-long greyouts of vision, the condition that needs to be excluded is idiopathic intracranial hypertension (IIH) — raised pressure inside the skull with no tumour to explain it. It is often mislabelled chronic migraine, partly because the two genuinely can look identical on a headache questionnaire, and partly because the sign that separates them is not in the headache history at all. It is at the back of the eye. This is one of the specific scenarios I have in mind when I write about headaches that are not getting better despite treatment.
The symptoms that make me stop calling it migraine
Three things shift my thinking, and the first one is the most useful because patients almost never think it matters enough to report.
- Pulsatile tinnitus. A whooshing or swooshing sound synchronised with the heartbeat, frequently in one ear, often changing when you turn your head or press lightly on the side of the neck. Roughly six in ten patients with IIH describe it. It is distinctly uncommon in migraine.
- Transient visual obscurations. Vision in one or both eyes greys, whites or blacks out for a few seconds, typically when standing up, bending over or straining. This is not migraine aura. Aura builds over minutes, drifts across the visual field, and usually brings positive phenomena — zigzags, shimmer, sparkle. An obscuration is abrupt, brief and visually uninteresting: the lights simply go out and come back.
- A pressure-shaped headache. Worse on waking or after lying flat, aggravated by coughing, straining or bending forward. Migraine also dislikes movement, so this alone decides nothing — but alongside the first two it becomes hard to ignore.
Add to that list new horizontal double vision from a sixth nerve palsy, neck and back pain, and — critically — peripheral visual field loss that the person cannot detect in themselves. It is worth noting that the mirror-image problem exists too: a headache that appears only on standing and vanishes on lying down usually means low pressure rather than high, which I cover in the piece on orthostatic headache and spontaneous intracranial hypotension.
IIH is most common in women of reproductive age carrying excess weight, and recent weight gain is a frequent trigger. But I have diagnosed it in thin women, in men, and in teenagers. Expecting the textbook body habitus is one of the main reasons it gets missed.
Why a “normal MRI” does not rule this out
This is the part that costs people years. IIH involves no mass and no bleed. The scan is supposed to look broadly normal. A report of “no acute intracranial abnormality” tells you nothing whatsoever about the pressure inside the skull — it answers a different question, the one about tumours and haemorrhage that I address in what actually worries a neurologist about headache.
A radiologist who has been told to look for raised pressure may comment on an empty or partially empty sella, flattening of the back of the eyeball, distension or tortuosity of the optic nerve sheaths, or narrowing of the transverse venous sinuses. Those findings support the diagnosis. Their absence does not exclude it, and their presence alone does not confirm it. Incidental findings on headache MRIs are a recurring theme — the same logic applies to the white matter spots so many migraine patients are alarmed by.
The actual gatekeeper is a dilated look at the optic discs. Papilledema — swelling of the optic nerve head where the raised pressure is transmitted forward — is the cardinal sign, and it cannot be reliably excluded by a quick glance through an undilated pupil in a busy clinic. So the question I would ask is narrow and specific: has anyone examined my optic discs with my pupils dilated? If the answer is no, and it often is, that is the commonest single reason IIH goes undiagnosed.
What I request is a formal ophthalmology assessment: dilated fundoscopy, OCT imaging of the retinal nerve fibre layer, and automated perimetry. Field loss in IIH begins peripherally and nasally — precisely where the brain fills in the gap and you notice nothing until a great deal has gone.
The mimic you cannot afford to miss
Before anyone uses the word “idiopathic,” cerebral venous sinus thrombosis has to be ruled out. A clot obstructing the brain’s venous drainage raises intracranial pressure and produces a nearly identical clinical picture — but it is treated with anticoagulation, and missing it is dangerous. Ruling it out requires MR venography or CT venography, not a plain MRI. I order venous imaging in every new suspected case, without exception.
Secondary causes also have to be asked about directly, because several are common and reversible: tetracycline antibiotics such as doxycycline and minocycline (frequently prescribed for acne, in exactly this demographic), vitamin A derivatives including isotretinoin, high-dose vitamin A supplements, lithium, growth hormone, and withdrawal from a course of corticosteroids. Anaemia, obstructive sleep apnoea and thyroid disease belong on the same checklist.
Then the pressure itself is measured, by lumbar puncture, with the patient lying on their side. Measured sitting up, the number is meaningless. In adults, an opening pressure above about 25 cm of CSF with otherwise normal CSF composition supports the diagnosis. Two caveats I state out loud to every patient: pressure fluctuates through the day, so a single borderline reading does not overturn unmistakable papilledema — and a high reading in someone with no papilledema and no other sign does not by itself make them an IIH patient. I have watched both errors send people down the wrong road for a year.
Why the migraine treatment you were given may have made things worse
Acetazolamide is first-line. It is a carbonic anhydrase inhibitor that reduces CSF production, and in the Idiopathic Intracranial Hypertension Treatment Trial it produced a modest but real improvement in visual field function when paired with a weight-management programme. The dose is titrated upward; tingling in the fingers and a flat metallic taste to carbonated drinks are expected effects rather than reasons to abandon it.
Weight reduction of roughly five to ten per cent of body weight is genuinely disease-modifying in patients who are overweight. I say that without moralising, and I try to say it the same way I would say it about blood pressure: this is a mechanical pressure problem, and body mass alters the pressure. Topiramate is a defensible alternative or addition, since it carries weak carbonic anhydrase activity and tends to reduce appetite — which is why it fits this condition better than most preventives, though the side effects worth knowing about in advance still apply.
Here is the part that stings. A conventional chronic-migraine pathway often begins with amitriptyline or a similar agent that causes weight gain, and a patient with undiagnosed IIH can get measurably worse on it. Stack daily analgesics on top of a daily headache and medication-overuse headache arrives as a third layer. Two years of apparent preventive failure can be manufactured this way, and none of it is the patient’s fault.
When vision is threatened, we escalate — venous sinus stenting, optic nerve sheath fenestration, or CSF diversion by shunt — decided jointly with ophthalmology and neurosurgery, and decided quickly. One honest caveat: normalising the pressure does not always end the headache. Migraine and IIH coexist frequently, and some patients need both conditions treated. I say this at the first visit so that a lingering headache afterwards does not get read as failure.
When this becomes an emergency for your eyes
Vision that is deteriorating week on week, new double vision, or obscurations happening many times a day should be seen by an ophthalmologist within days, not slotted into a routine referral queue. Fulminant IIH progresses over weeks and can take sight permanently. Around one in ten patients ends up with significant irreversible visual loss, and that fraction sits overwhelmingly among those diagnosed late.
The headache is what brings people to my office. The vision is what I am actually racing. So if you are being treated for chronic migraine, and you can hear your pulse in your ear, and your sight briefly goes out when you stand — bring those two details to your next appointment and ask the narrow question about your optic discs. Everything else follows from the answer.
Next steps
- Free red-flag checklist. Print the warning signs that mean a headache needs assessment now, not next month: Headache Red Flags Checklist.
- Talk to a specialist. If your headaches are not responding to treatment and something in this article sounded familiar, book a consultation.
Written by Dr. Tae-Ho Guak, MD, board-certified neurologist with 25 years of clinical practice and over 100,000 patients seen.
Medical disclaimer: this article is general educational information and is not a substitute for individual medical advice, diagnosis or treatment. Do not start, stop or change any medication on the basis of what you read here. If you have sudden severe headache, new visual loss, double vision, weakness, confusion, fever with neck stiffness, or headache after head injury, seek emergency medical care.
From the textbook. Chapter 42, “Disorders of Intracranial Pressure,” of my clinical textbook Headache Medicine covers this topic in full for doctors, with the evidence and decision pathways behind it. About the book →