Case 9. Weakness and tingling
What is the lesion?
This question is always best-answered using the tempo of development, with some additional information helping to further qualify the suspected cause - including what lesions tend to affect certain areas, and any associated demographic or comorbidity-related risk factors the patient may have.
However, tempo of onset can be difficult When people wake up in the morning with symptoms. They are often reported as sudden-onset – but we can’t say definitively this is correct. They might have been building up over hours and the patient then became aware of them on waking. This is obviously different if the patient had just had a short nap!
This isn't just an academic question - for a long time it posed a major barrier to reperfusion therapy in strokes presenting on waking up, and was a contraindication to treating. We now can tackle this using advanced imaging techniques that 'age' the stroke and assess viability. However, for most situations this doesn't apply and we have to just accept the available information.
While we don’t have the same useful information we might have for symptoms that come on during waking hours, we can tell something about wake-up lesions from what happens next.
Here, we know the patient’s clinical course didn’t change during a 48 hour admission; it just stayed the same. That means the problem was maximal from the start - and the severity was only mild, with partial sensory reduction and mild weakness not bad enough to seriously impact on mobility.
This suggests a vascular lesion – abrupt onset, fixed in distribution rather than spreading, maximal in intensity from the start, and also, entirely compatible with the anatomical distribution described. This would be a classic presentation for a lacunar infarction of the posterior limb of the internal capsule. A deep haemorrhage into the capsule and surrounding structures might also present like this. The patient also has significant vascular risk factors present so is a prime candidate for an ischaemic or haemorrhagic stroke. Note also that while strokes tend to largely cause negative symptoms, the tingling doesn’t exclude stroke – despite being a ‘positive’ symptom, people do frequently experience this.
Could it be anything else? There are other causes of stroke-like presentations and the short time frame here could potentially fit some:
It seems too quick and fixed for a tumour or a degenerative condition, and the unilateral and highly focal features go against a toxic/metabolic cause (such as osmotic demyelination in the central pons) - such conditions don't lateralise like this and are usually symmetrical.
A stroke seems by far the most likely cause.
Clinical formulation