Impact of Herniation on WFNS Grading and Outcome in Spontaneous Subarachnoid Hemorrhage - a SWISS SOS Observational Trial

Background

Aneurysmal subarachnoid hemorrhage (SAH) is a severe disease affecting approximately 400 patients per year in Switzerland. Death and severe disability after spontaneous SAH are related to the initial severity of the bleeding. The scale which is most often used and recommended to grade the severity of SAH is the World Federation of Neurosurgical Societies scale. Besides the Glasgow Coma Scale as basis for the WFNS grading, the existence of a neurologic deficit is included in this scale. In general WFNS I-III patients are termed good grade and WFNS IV and V poor grade. Morbidity and Mortality after SAH should increase with higher WFNS grade. Yet, despite low Glasgow Coma Scale (GCS) scores in poor grade SAH, 35 to 50% of aggressively treated patients show a favorable outcome.Even in the most severe SAH, i.e. WFNS grade V, a good outcome is observed in 24 to 50% of patients treated aggressively, which limits the usefulness of this scale for decisions such as whether to withhold or continue treatment. Especially the differentiation between WFNS grade IV and WFNS grade V in intubated patients is a huge problem. The reason for the discrepancy between poor grading and favorable outcome is due to the difficulty of reliable GCS assessment in the acute stage of SAH. In the acute stage the clinical status of the patient is distorted due to sedative medication, seizure and hydrocephalus and does not necessarily display the "real" clinical status. Therefore favorable outcome in poor grade SAH patients is not a matter of a very beneficial course, but rather of an initial wrong WFNS grading.

The necessity of a reliable WFNS grading becomes evident when clinical decisions are made on this basis or when scientific data of different studies has to be compared. With respect to clinical decisions - usually WFNS grade V patients are not being treated due to the limited capacity of surviving the SAH. Up to now there is no validated triage scheme to identify which SAH patients will most likely not benefit from aggressive treatment based on WFNS scores.

Because the GCS is the basis for WFNS grading, information about progressive herniation beyond the motor response and posturing - e.g. third nerve dysfunction or loss of brain stem reflexes - is unfortunately not incorporated in routine SAH grading. As a known consequence, sedated and ventilated patients who do not exhibit a motor response but have symmetrically reactive pupils and intact brain stem reflexes may be wrongly classified as having a GCS score of 3 and thus a WFNS grade V, which leads to inaccuracies in the prognostic power of the WFNS in poor grade patients.

In this study, the investigators will apply the concept following the logic of the original GCS design and the pathophysiological concept behind the scale. During progression of brain herniation, abnormal flexion (decorticate rigidity, late diencephalic syndrome) is followed by abnormal extensor posturing (decerebrate rigidity, mesencephalic syndrome). Both are positive signs, i.e. signs that can be observed by the examiner. If herniation further progresses, damage occurs to the medulla and typical signs are flaccidity, no response to pain, mydriasis and no reaction to light. Using the latter "positive" signs would help to verify a true GCS 3 patient.