Intracranial hypertension

The brain sits inside a rigid box with no spare room. It is surrounded by cerebrospinal fluid, which is produced continuously and reabsorbed just as continuously. If more fluid accumulates than leaves, or if something appears inside the skull that should not be there — blood, pus, a tumour, swelling — the pressure rises, because that volume has nowhere to expand into. This is what intracranial hypertension means. Sometimes the cause is obvious; sometimes a full investigation turns up nothing at all, and then we speak of the idiopathic form, which is what this page covers in most detail.

How it shows itself

The complaints fall into two groups: headache and vision. It is the second that makes the condition serious.

• Headache, usually daily and bursting in quality, worse in the morning and on waking, made worse by coughing, sneezing, straining and bending forward, and often easier on standing up;
• brief episodes of dimmed or greyed-out vision, lasting seconds, more often in one eye, commonly on standing or bending. This is the most worrying of the early signs and is far too easily put down to tiredness;
• a noise in the ears in time with the pulse, heard mostly in quiet surroundings and at night;
• nausea and vomiting, often in the morning;
• double vision, typically on looking to the side, because the nerve that turns the eye outwards is affected;
• narrowing of the visual field, starting at the edges, which is why it goes unnoticed until something important disappears;
• neck and back pain, pain on moving the eyes, discomfort in bright light;
• drowsiness, irritability, difficulty concentrating.

Confusion, increasing drowsiness, weakness of an arm or leg and loss of sensation are uncommon in the idiopathic form and always call for urgent assessment: something more dangerous is usually raising the pressure.

When to call an ambulance

Call an ambulance — in Spain, Italy, Portugal, Poland and Ukraine on the single European number 112 — or go straight to an emergency department if:

• the headache came on suddenly and reached full intensity at once, like a blow;
• fever, a stiff neck or a rash have joined the headache;
• confusion, unusual drowsiness or a seizure have appeared;
• an arm or leg has become weak, the face has dropped on one side, or speech has become slurred;
• vision has deteriorated sharply or been lost;
• a severe headache begins after a blow to the head, even hours or days later.

Rapidly worsening vision in someone already diagnosed is an emergency too: there the count is not in months of monitoring but in days until intervention. A headache building gradually alongside a new noise in the ears does not need an ambulance, but it does need an appointment within a few days.

Why the pressure rises

Doctors first look for an obvious cause, because it changes the treatment entirely:

• severe head injury, bleeding into the brain, a ruptured aneurysm, a stroke with extensive swelling;
• a brain tumour, an abscess, meningitis, encephalitis;
• hydrocephalus, a disturbance in the circulation of cerebrospinal fluid;
• cerebral venous sinus thrombosis, a clot in the veins draining blood from the brain. This point is pivotal: the thrombosis produces a picture indistinguishable from the idiopathic form but is treated differently and is dangerous if missed, so it is excluded in everyone;
• severe uncontrolled high blood pressure, heart and lung disease with carbon dioxide retention, sleep apnoea.

The idiopathic form is diagnosed once all of the above has been ruled out. It is uncommon and affects mainly women between twenty and forty, more often those carrying excess weight or who have gained weight noticeably in recent times. What else it has been linked with:

• medicines: tetracycline antibiotics, including those given in long courses for acne; vitamin A preparations and retinoid derivatives; lithium; growth hormone; withdrawal of steroids after prolonged use; in children, an excess of thyroid hormone during treatment;
• too much vitamin A from supplements;
• iron deficiency anaemia and other severe anaemias;
• hormonal disorders such as adrenal insufficiency, underactive parathyroid glands and polycystic ovary syndrome;
• systemic lupus erythematosus and other autoimmune diseases;
• chronic kidney disease.

Go through your list of medicines and supplements before the appointment and bring it along: sometimes the whole treatment begins with stopping one product.

How it is confirmed

The diagnosis is assembled from several parts, and none of them stands on its own.

First and most important is examination of the back of the eye with the pupil dilated. When pressure is raised, the optic disc swells, and that swelling is visible. It is not unusual for an optometrist to spot it first during a routine sight test — if you have been told that your discs "look unusual", that is not a trifle and a neurologist should be seen without delay. The assessment is completed by visual field testing and by optical coherence tomography, which puts a number on the swelling and allows it to be tracked over time.

Imaging comes next: magnetic resonance scanning that must include a study of the venous sinuses, that is, venography, or computed tomography with contrast. The purpose of this stage is not to "see the pressure" but to exclude a tumour, hydrocephalus and venous thrombosis.

If the scans are clear, a lumbar puncture follows: a needle placed between the lumbar vertebrae measures the pressure of the cerebrospinal fluid and takes a sample for analysis. This is the only way of confirming that the pressure really is raised, and at the same time it rules out infection and inflammation. Idiopathic intracranial hypertension is diagnosed only when the pressure is high, the composition of the fluid is normal and no cause has been found.

Why it matters

The idiopathic form poses almost no threat to life, but it poses a very real one to sight, and that is where the whole point of treatment and monitoring lies. Swelling of the optic nerve, if it persists, destroys fibres, and visual field once lost does not come back. The treacherous part is that the process advances silently: acuity measured on a letter chart stays good for a long time while the field is already narrowing at the edges. That is why regular eye checks are arranged even for people who notice nothing, and they must not be skipped.

The other side is the headache. It can persist even after the pressure has settled, and it is then treated separately, as a chronic headache. There is a trap here: taking painkillers every day keeps the headache going by itself. It is worth raising with your doctor.

The condition often runs for years and in some people returns after a remission. Report any new change in vision at once — that is what the whole monitoring arrangement exists for.

How it is treated

Treating the secondary forms means treating their cause: dealing with the clot, the tumour or the infection, or withdrawing the drug responsible. In the idiopathic form the approach is different.

Weight loss. This is the only measure with a proven effect on the course of the disease rather than on the symptoms alone. Losing even part of the excess weight reduces disc swelling and headache in many people and sometimes brings a lasting remission. It makes sense to do it with support, from a dietitian; where obesity is marked, both medicinal and surgical routes to weight loss are discussed.

Medicines. The mainstay is a drug that reduces the production of cerebrospinal fluid, from the carbonic anhydrase inhibitor group. Side effects — tingling in the fingers and around the mouth, an odd taste to fizzy drinks, tiredness — are common but usually tolerable, and the dose is built up gradually. Other diuretics may be added. Steroids are used only briefly, as a bridge when sight is threatened and an operation is pending: taken for long they add weight and cause symptoms to rebound on withdrawal, which works against the main treatment.

Lumbar punctures. Draining off some fluid during a puncture relieves the headache quickly, but the effect does not last, so it serves as temporary help rather than as treatment.

Surgery. It is considered when sight is deteriorating or drugs are not coping. A shunt is a fine tube carrying excess fluid from the brain ventricles or from the lumbar region into the abdomen; it helps both the pain and the pressure, but shunts block and move, and repeat operations are not rare. Optic nerve sheath fenestration means cuts in the covering around the nerve to take pressure off it specifically; it is aimed at saving vision and does little for headache. In selected cases, where a narrowing of a venous sinus is found, placing a stent in that vein is discussed. Every option carries its own risks, and the choice is made together with a neurosurgeon and an ophthalmologist, according to what most needs protecting in your case.

Online consultation

An online appointment fits at two points. Before the diagnosis, the doctor will work through the character of the headache: when it is worst, whether it depends on posture and straining, whether there is a pulsing noise in the ears, whether there have been episodes of vision greying out or doubling. They will go through your medicines and supplements with you, weigh up other possible causes, and explain which investigations come first and why looking at the back of the eye cannot wait. If the diagnosis is already made, the appointment is a good place to discuss how you are tolerating the drugs, the weight-loss plan, what to do if the headache worsens, and which changes in vision mean you must not wait for the scheduled review. An online consultation cannot fully replace a hands-on eye examination, but it does stop you losing time before one.

This material is for information only and does not replace medical advice.