Continuing our series on clinical scenarios that may be mishandled in primary care, Dr Toni Hazell explains that headache is very rarely caused by hypertension
A 43-year-old female patient presents with recurrent headache episodes that she believes are due to her hypertension, diagnosed a year earlier. She says there are no particular triggers for the headaches, but that they seem to have got worse over the past year. She has noticed her blood pressure readings are higher during a headache and requests referral.
The reality
Hypertension does not usually cause headache.
The issue
It is a common urban myth that a raised blood pressure causes headaches, and it is not uncommon for someone with a headache to check their blood pressure (BP). As doctors, it is important we understand that raised BP rarely causes a headache, and giving credence to this belief will reinforce it in the minds of our patients and risks subjecting them to over-investigation and possible overdiagnosis.
The evidence
Hypertension rarely has any noticeable symptoms.1 We treat it because it is a major risk factor for stroke and other cardiovascular disease, not because hypertension itself makes the patient feel unwell. Apart from rare secondary causes, or associated pathologies, none of the relevant guidelines or bodies mention headache as a presentation – these include NICE2, SIGN3, the European Society of Cardiology4 and the British Heart Foundation.5
It is much more likely the causation is the other way round – any pain can activate the sympathetic nervous system and cause a rise in blood pressure. This includes headache and it is generally unwise to do a routine BP check in a patient who is experiencing acute pain, or to do so immediately after a painful procedure such as an injection.
Anxiety is often linked with tension headaches, and can also cause a rise in BP (leading to the well-known phenomenon of ‘white coat hypertension’). As a consequence, patients with anxiety may also make a false connection between a headache and raised BP.
Avoiding a clanger
A patient who calls you with a concern about headache and hypertension can often be dealt with on the phone. If there are no red flags, and the headache sounds like something benign (for example, a tension headache) or is a flare of a known condition such as migraine, then reassurance and simple advice might be sufficient.
Avoid checking the patient’s BP as it is likely to be raised and this risks overdiagnosis of hypertension or unnecessary investigations. Explaining this to patients can help prevent them from checking their BP at home when they have a headache. The whole practice team should be aware of this misconception and be able to give sensible advice to patients.
Caveats
There are two presentations to be aware of. The first is in patients who have a phaeochromocytoma causing the headache and raised BP. These are rare tumours of the adrenal gland, which would present with a headache and other symptoms including palpitations, sweating, anxiety and fluctuating BP.6 The second is in malignant hypertension, defined as a BP higher than 180/120mmHg with end-organ damage – a headache might be present due to cerebral damage, although this is not always the case.7 A suspicion of malignant hypertension or a phaeochromocytoma should prompt a same-day review in secondary care.
Another complicating factor is that antihypertensives can cause headache as a side-effect. It is listed as a side-effect in the BNF for some calcium channel blockers, thiazide diuretics, ACE inhibitors and angiotensin receptor blockers. As with all new symptoms, it is therefore important to ask the patient about any new medication, and whether there was any link timewise between starting the medication and the new symptom, as well as whether the symptom is resolved by stopping the medication.
Key points
- High blood pressure does not usually cause a headache – the causality is more likely to be the other way around
- If a serious cause of hypertension is suspected (such as malignant hypertension) then same-day review in secondary care is advised
- Many medications used to treat hypertension can cause a headache as a side-effect
Dr Toni Hazell is a GP in north London
References
- NHS. Overview: Hypertension. 2019. Link
- NICE. Hypertension in adults: diagnosis and management, 2022. NG136. Link
- SIGN. Risk estimation and the prevention of cardiovascular disease. Glasgow: Healthcare Improvement Scotland, 2017. Link
- Williams B, Mancia G, Spiering W et al. Guidelines for the management of arterial hypertension. Eur Heart J 2018; 39:3021–104 Link
- British Heart Foundation. High blood pressure. London: BHF. Link
- Cancer Research UK. What are phaeochromocytomas? 2022. London: CRUK. Link
- Naranjo M, Chauhan S, Paul M. Malignant Hypertension. In: StatPearls [Internet]. Treasure Island, US: StatPearls Publishing, 2022. Link
I recently saw a patient who had been managed over the phone with headaches but did have malignant hypertension and was admitted. It is always worth asking the patient to check their BP at the pharmacist so we don’t miss the rare but serious diagnosis.
Thank you Toni, interesting observation. I had always been taught that waking or morning headache was a significant symptom in hypertension. Whilst the pathophysiology remains uncertain, I think I would still advise a check on BP, even if headache was the only presenting symptom. If raised during a consultation, I would loan a machine for a series of BPs to be taken at home or arrange an ambulatory test to check for a normal night dip, were there some persisting doubt. I think it is reasonable to say that there is ample evidence that early management and treatment of hypertension by general practitioners will improve cardiovascular outcomes.