Recently I attended a patient whose presentation challenged many of the assumptions we routinely make when confronted with sudden neurological deficit. As paramedics, when we hear the word “stroke”, our minds immediately focus on the brain – FAST assessments, facial droop, speech disturbance, large vessel occlusions and thrombolysis windows.
It wasn’t until I received an email from a colleague – thanks Matt – who transferred the patient to the hyperbaric chamber for further treatment with a diagnosis of a spinal stroke, reminded me that not all strokes occur above the foramen magnum.
The Case
The patient was an older female who developed sudden onset severe back pain followed by rapidly progressive weakness of both lower limbs. She woke with an urge to urinate, walked to the toilet, then returned to the bedroom when she experienced sudden bilateral leg weakness, where her husband assisted back to bed. There was no history of trauma or previous back problems, no obvious musculoskeletal cause and, importantly, no facial asymmetry, speech disturbance or upper limb deficit. To be honest, towards the end of a long 13-hour shift, stroke was not one of my differentials that came to mind first.
Observations were unremarkable, apart from a mild tachycardia of around 110 bpm. Medications included three different blood thinners and had recently (a month ago) undergone surgery for a pseudoaneurysm – a AAA was also mentioned as part of her medical history according to her last hospital discharge paperwork. She was also due for her regular dialysis appointment in a couple of hours.
Assessment wise, it was noted that there was bilateral lower limb weakness, with no patient movement or reflexes to both legs with altered sensation to the left leg, and no sensation to the right leg. The patient also described both thighs feeling swollen.
Initially, several more common diagnoses came to mind:
- Spinal cord compression, potentially from a leaking or ruptured AAA;
- Disc prolapse;
- Cauda equina syndrome;
- inflammation or tumour; or
- Functional neurological disorder
However, the abrupt onset and progression of symptoms suggested a vascular event rather than a mechanical one, but no firm diagnosis was decided upon – so I did what paramedics are good at – documenting the findings; managing the symptoms and transporting to hospital. Intravenous access was gained (with the usual difficult cannulation associated with a dialysis patient) and effective analgesia achieved with IV fentanyl.
Rare, But Real
Spinal cord infarction is uncommon, accounting for less than 1.25 per cent of all strokes – that’s less than 500 spinal strokes occurring in all of Australia each year. Unlike cerebral strokes, most clinicians will encounter very few cases during their careers. The rarity contributes to delayed recognition and frequent misdiagnosis.
The spinal cord receives blood supply from the anterior and posterior spinal arteries, supplemented by radicular arteries along its length. Interruption of this blood supply (either from a clot or haemorrhage) can result in sudden ischaemia of the cord and rapid neurological dysfunction.
Presentation: The Clues We Shouldn’t Miss
What struck me most was how “un-stroke-like” the patient appeared. With the usual hindsight, and a little research, a spinal stroke should have been an obvious differential, but in a caffeine-withdrawn brain at 5am I’ll admit I didn’t think of it – my primary thought was a leaking aneurysm putting pressure on the nervous system.
There was:
- Sudden severe back pain;
- Bilateral lower limb weakness;
- Sensory changes;
- Preservation of cranial nerve function;
- No speech disturbance;
- No facial weakness.
Many patients with spinal cord ischaemia experience acute neck or back pain at symptom onset, often localised to the level of injury. Neurological deficits can develop within minutes, producing an acute myelopathy (compression or injury of the spinal cord).
This differs markedly from the classic FAST-positive cerebral stroke patient we are trained to identify. Even the BEFAST (balance loss; eyes; face drooping, arm weakness; speech difficulty and time) rapid screening tool is not specifically tailored to identify spinal strokes, however the inability to stand could be argued that as a loss of balance.
The Diagnostic Trap
Had this patient developed arm weakness and dysarthria, a stroke pathway would have been activated immediately.
Instead, the presentation sat awkwardly between neurological, vascular and spinal pathology.
This is where clinical reasoning becomes important.
When assessing patients with sudden neurological deficit, consider:
- Is the onset abrupt?
- Is there a vascular pattern to the symptoms?
- Are deficits bilateral?
- Is there associated severe back or neck pain?
- Is there a clearly defined sensory level?
- Are cranial nerves spared?
A spinal stroke may not fit our traditional stroke screening tools, yet it remains a time-critical neurological emergency.
What Can We Do Pre-Hospital?
The reality is that definitive diagnosis requires advanced imaging. Pre-hospital clinicians are unlikely to diagnose spinal cord infarction with certainty.
However, we can recognise that something serious is occurring.
The goals become:
- Early identification of acute neurological deficit;
- Thorough neurological examination;
- Documentation of symptom onset time;
- Identification of progression of symptoms;
- Exclusion of hypoglycaemia and other mimics;
- Rapid transport to an appropriate facility;
- Clear communication of findings during handover.
Perhaps most importantly, we should resist the temptation to prematurely label unusual presentations as musculoskeletal problems.
For those thinking about the transfer to the hyperbaric chamber – Hyperbaric Oxygen Therapy (HBOT) is used to aid recovery from spinal strokes by enhancing tissue oxygenation and reducing inflammation in the spinal cord. It involves placing the patient in a pressurised chamber and inhaling high or pure oxygen at higher than atmospheric pressure to improve dissolved oxygen in the blood to relieve symptoms.
Reflection
The case reinforced a lesson that many years in emergency care continue to teach: common things are common, but rare things still happen.
Cognitive shortcuts are useful until they are not.
When a patient presents with sudden onset neurological deficit, we should keep an open differential diagnosis and remember that the central nervous system extends well beyond the brain.
The spinal cord may be hidden from view, but occasionally it becomes the site of a devastating vascular event.
The next time you encounter a patient with sudden weakness, sensory changes and severe back pain, ask yourself:
“If this isn’t a disc, what else could it be?”
Sometimes the answer may be a stroke where you least expected to find one.
“Not every stroke is FAST positive. Sometimes the clues are found in the spine rather than the face.”