In this post, I’m going to run through ten of the rarer stroke types, ordered from the least rare down to the rarest. For each one I’ve given the approximate share of all UK strokes it represents, and a rough number of people affected each year, working from the figure of roughly 100,000 strokes annually in the UK. Two caveats: some of these are measured as a proportion of all strokes and others as a cause of stroke in a particular group, so the figures aren’t all counting the same thing; and for the very rarest, UK-specific data is thin… so those numbers are estimates rather than firm counts:
- Subarachnoid haemorrhage (SAH), around 5% of all strokes, so roughly 5,000 UK cases a year. It’s a bleed into the space around the brain, usually from a ruptured aneurysm, and it presents differently from most strokes: a sudden, severe ‘thunderclap’ headache, often described as the worst of a person’s life, sometimes with neck stiffness, vomiting and/or collapse. It affects a younger average age than ischaemic stroke and is a serious neurosurgical emergency.
- Cervical artery dissection (CAD), roughly 2% of all strokes, so around 1,500 to 2,000 UK cases a year, yet responsible for up to a quarter of ischaemic strokes in people under 50. It’s a tear in the inner lining of a carotid or vertebral artery in the neck; blood enters the vessel wall, a clot can form, and a stroke follows. It can follow major trauma, but also something minor, like a sharp turn of the head, a sports injury, occasionally a hairdressing appointment or a heavy coughing fit.
- Spinal cord stroke (SCS), around 1% of all strokes, so in the region of 1,000 UK cases a year. Stroke is usually thought of as a brain event, but the spinal cord has its own blood supply and can suffer the same injury. Rather than affecting the face or speech, it affects movement and sensation below the level of the injury; sudden loss of use of the legs, for instance, or loss of temperature and pain sensation while other sensations are spared. Because it doesn’t resemble a typical stroke, it’s one of the most commonly misdiagnosed.
- Cerebral venous sinus thrombosis (CVST), well under 0.5% of all strokes, so roughly 200 to 270 UK cases a year. An ordinary ischaemic stroke involves a blocked artery carrying blood to the brain; CVST is the reverse, a clot in the veins that drain blood away from it. It occurs in a different population from most strokes: younger adults, and women around three times more often than men, with associations including pregnancy, the combined contraceptive pill and clotting disorders. Early symptoms are often vague btw, so it’s frequently taken for migraine at first.
- Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), an inherited small-vessel disease, with a UK prevalence usually cited at around 2 to 5 per 100,000 people, so on the order of a few hundred affected individuals nationally and a small annual share of strokes. Caused by a fault in the NOTCH3 gene, it produces recurrent small deep strokes from mid-life, often alongside migraine with aura, mood disturbance and a gradual decline in thinking. It runs in families, and a parent with CADASIL passes it to each child with a one-in-two chance.
- Moyamoya disease (MMD), with a Western incidence of roughly 0.09 per 100,000 per year, so perhaps 50 to 100 new UK cases a year across all ages. The name describes the ‘puff of smoke’ appearance on angiography as the main arteries at the base of the brain narrow and the body grows a fragile network of tiny compensating vessels. It causes strokes in both children and young adults, is more common in East Asian populations, and often needs surgery to reroute blood supply.
- Fibromuscular dysplasia (FMD)-related stroke, rarer still as a cause of stroke, though FMD itself is under-recognised. FMD is an abnormal development of the artery wall, most often in the arteries to the kidneys and the neck; when the neck arteries are involved it can lead to dissection, aneurysm and stroke, typically in women under 50. Precise UK stroke numbers aren’t well established, but as a stroke cause it well below 0.5%.
- Stroke from a cardiac myxoma, a rare benign tumour of the heart. Fragments of the tumour, or clots forming on it, can break off and travel to the brain. Cardiac myxoma affects roughly 0.5 per million people a year, so only a handful of UK strokes annually arise this way; and actually, the stroke can be the first sign the tumour exists at all.
- Stroke from central nervous system (CNS) vasculitis, inflammation of the blood vessels within the brain itself. It’s genuinely rare, with primary CNS vasculitis (PCNSV) estimated at around 2.4 per million per year, so a small number of UK strokes a year. It can cause headache, cognitive change and strokes in people with no conventional vascular risk factors, and it’s one of the hardest diagnoses to reach, often needing specialist imaging or biopsy.
- Stroke from an air or fat embolism, where a bubble of air or a globule of fat, rather than a blood clot, blocks a cerebral vessel. Air embolism can follow certain medical procedures or diving accidents; fat embolism (FES, fat embolism syndrome) most often follows major long-bone fractures. Numbers are tiny and not reliably counted, but as a stroke mechanism it’s about as uncommon as they come.
So there it is – these ten all are managed within the same specialist stroke and neurosciences services as any other stroke, with the same rapid assessment and imaging. But because they affect younger people predominantly, present with unusual symptoms or fall outside the FAST template, they’re more often diagnosed late… and we know too well that ‘delay costs brain’…
