Stroke Recovery Calculator

How does this stroke recovery calculator work?

This health tool determines prognosis of stroke recovery as an easy to interpret percentage based on three parameters:

■ NIH stroke score – the National Institutes of Health Stroke Scale (NIHSS) score measured at the time of scanning;

■ Time from stroke onset;

■ DWI lesion volume (diffusion-weighted imaging) – the extent of the ischemic brain injury and the integrity of the corticospinal tract as revealed by MR DWI within 36 hours of stroke onset.

The first parameter in the stroke recovery calculator takes the score from the NIH stroke scale. This measures neurological function in patients where stroke is suspected or already diagnosed. It comprises of an examination performed by a medical professional aimed at checking left and right motor and cortical function. There are 11 items assessed and the result quantifies stroke severity during the first evaluation. Subsequent evaluations with NIHSS are done to track any changes.

After stroke onset (starting from 12 hours and moving towards 7 days), most uncomplicated cases experience improvement in neurologic impairments. On a medium to long term, most recovery takes place between the first 3 to 6 months.

DWI is sensitive in early detection of small infarcts with reported sensitivity ranges from 88 - 100% and specificity ranges from 86 - 100%.

Excessive corticospinal tract injury is a predictor of poor recovery.

Other studies have forwarded data suggesting that functional outcome at the 3 month evaluation predicts 4 years survival and that functional status at the 6 month evaluation prognoses long term survival.

The model benefits from external validation that has proven 0.77 sensitivity and 0.88 specificity. The three parameters are found to provide a better prediction than each of the parameters alone, therefore the clinical scale was made available for use.

The most common physical problems after stroke include:

■ Weakness in limbs;

■ Paralysis;

■ Muscle spasticity;

■ Increased sensitivity to pain;

■ Numbness or tingling.

Cognitive problems occur with different degrees of severity with the areas to be affected being short term memory, perception, aphasia and attention.

Other effects of stroke include fatigue unrelieved by rest and visual loss.

The Gold Standard is stroke IV treatment with tPA (tissue Plasminogen Activator) which dissolves the clot and improves blood flow to the brain. Early administration of tPA also influences the recovery rates.

The second most common treatment option includes the removal of the clot through an endovascular procedure with the help of a catheter.

Score interpretation

The original predictive model for recovery identifies 3 likelihood levels:

■ 0 - 2 points: 7%;

■ 3 - 4 points: 46-53%;

■ 5 - 7 points: 87-91%.

Hemorrhagic stroke has poorer prognosis than ischemic stroke and poses a higher risk of developing complications. The ischemic stroke is reported in the US to make 85% of all strokes.

Data suggests that most survivors gain functional independence with 25% of survivors of stroke being left with minor disability while 40% showing more severe disabilities.

The modified Rankin Scale and the Barthel Index are two outcome tools that assess functional independence with aspects of self-care and dependency on help.

References

1) Baird AE, Dambrosia J, Janket S, Eichbaum Q, Chaves C, Silver B, Barber PA, Parsons M, Darby D, Davis S, Caplan LR, Edelman RE, Warach S. (2001) A three-item scale for the early prediction of stroke recovery. Lancet; 357(9274):2095-9.

2) Srinivasan A, Goyal M, Al Azri F, Lum C. (2006) State-of-the-art imaging of acute stroke. Radiographics; 26 Suppl 1:S75-95.

3) Allen LM, Hasso AN, Handwerker J, Farid H. (2012) Sequence-specific MR imaging findings that are useful in dating ischemic stroke. Radiographics; 32(5):1285-97.

4) Jongbloed L. (1986) Prediction of Function After Stroke: A Critical Review. Stroke; 17(4).