The World Federation of Neurosurgical Societies (WFNS) score is a rapid, standardized tool used by medical professionals to assess a patient’s neurological condition following a specific type of stroke. This grading system provides an objective measure of the severity of the brain injury immediately upon presentation. By quantifying the patient’s level of consciousness and physical ability, the WFNS score helps classify the severity of the illness. This standardized assessment is fundamental for communicating the patient’s status and directing immediate treatment pathways.
Understanding Subarachnoid Hemorrhage
A subarachnoid hemorrhage (SAH) is a life-threatening event involving bleeding into the subarachnoid space surrounding the brain. This space lies between the arachnoid membrane and the pia mater, two of the protective layers covering the brain. The most frequent cause of a spontaneous SAH is the rupture of an aneurysm, a weakened and bulging area in a blood vessel wall. When this vessel bursts, blood rapidly fills the space, which can quickly increase pressure on the brain.
The sudden presence of blood irritates the brain and its linings, often leading to a characteristic “thunderclap headache,” described as the worst headache of their life. Because the resulting brain injury is time-sensitive, immediate and standardized clinical grading is necessary. A rapid assessment determines the urgency of intervention and guides initial stabilization efforts, such as securing the patient’s airway. The WFNS score provides an objective snapshot of the patient’s clinical status at diagnosis.
The Components of the WFNS Score
The WFNS grading system relies on two distinct clinical observations: the Glasgow Coma Scale (GCS) and the presence of any focal neurological deficit. The GCS is a widely accepted neurological scale that objectively measures a person’s level of consciousness by evaluating three areas of responsiveness. These areas are eye opening, verbal response, and motor response, each scored separately and then summed for a total GCS score. A score of 15 represents a person who is fully awake and alert, while the lowest possible score is 3.
The second component is the presence or absence of a focal neurological deficit, which most often refers to motor impairment. A deficit is noted if the patient exhibits weakness on one side of the body, such as hemiparesis, or a speech impediment like aphasia. The presence of this motor weakness significantly worsens the patient’s neurological grade. For example, two patients might have the same GCS score, but the one with motor weakness will be assigned a higher WFNS grade. This inclusion acknowledges that localized brain damage, separate from the overall level of consciousness, strongly influences patient outcome.
Interpreting the Five Grades
The WFNS score assigns patients to one of five grades, ranging from Grade 1 (mildest injury) to Grade 5 (most severe). These grades are directly tied to the level of consciousness determined by the GCS and the presence of motor deficits.
Grade 1 is assigned to patients who are fully alert (GCS 15) and have no noticeable motor deficits beyond a headache. Grade 2 patients are awake (GCS 13-14) but lack observable focal motor weakness. Patients with Grade 3 have the same level of consciousness (GCS 13-14) but are differentiated by the presence of a focal neurological deficit, such as weakness in an arm or leg.
Grade 4 patients show a reduced level of consciousness, falling into a GCS range of 7 to 12, which includes states of drowsiness or stupor. These patients may or may not exhibit a focal motor deficit, as impaired consciousness is the primary marker of severe injury. Grade 5 is the most severe category, reserved for patients in a coma with a GCS score of 3 to 6. This deep state of unconsciousness, with or without motor deficits, indicates an immediate threat to life.
WFNS Score and Patient Outcomes
The WFNS score is a powerful predictor of a patient’s functional outcome and survival. A direct correlation exists where a higher WFNS grade at admission is associated with a poorer prognosis. Patients presenting with Grade 1 or 2 are considered to have a good-grade hemorrhage, with a higher likelihood of a favorable recovery.
Conversely, patients classified as Grade 4 or 5 are categorized as having a poor-grade hemorrhage, indicating a substantially increased risk of mortality or severe disability. For patients in Grade 5, mortality rates during hospitalization can range from 48% to 63%. Despite these statistics, the score is not a definitive sentence, as some aggressively treated patients, even in Grade 5, have achieved good outcomes. The score acts as a framework, used alongside other factors like the amount of blood visible on imaging (often graded by the Fisher Scale), to help medical teams discuss expectations and decide on intervention strategies.