Subarachnoid Hemorrhage Hunt And Hess Scale

The grading system explained

This is a health tool that evaluates the severity of subarachnoid hemorrhage based on the presentation symptoms of the patient.

The scale developed in 1968 by Hunt and Hess, two US neurosurgeons, consists of 5 items. These, along with their associated grading and the mortality risk are summarized in table below:

The result predicts risk of poor outcome in patients with non-traumatic SAH and the higher the grade, the higher the mortality risk and the lower the survival chances.

The scale can be administered in all patients admitted with suspicion/ diagnosed with subarachnoid bleeding, that have been neurologically consulted, regardless of other comorbidities.

The main criticism of the method refers to the small differentiation between the symptoms that indicate grade I and those that indicate grade II, disproportionate to the 10% difference in mortality risk between the two grades.

Subarachnoid hemorrhage (SAH) guidelines

SAH is a type of spontaneous intracranial bleeding that is caused, in non-traumatic patients, most commonly by an aneurysmal or arteriovenous malformation AVM leakage or rupture but can also be caused by hemorrhage within the brain tissue (parenchyma).

These cases are life threatening and there is a mortality rate of 15-30% before the patient reaches hospital and another 25% during the first 24 hours after admission. Because of the high mortality risks, the importance of constant monitoring and application of sensitive prognostic methods cannot be stressed enough.

The most common risk factors for SAH include:

■ Old age;

■ Hypertension;

■ Arteriosclerosis;

■ Smoking;

■ Substance abuse;

■ Alcohol consumption;

■ Low levels of estrogen in menopausal women.

Before such an atraumatic vascular event occurs, there may appear a series of premonitory symptoms such as headaches, dizziness, orbital pain, visual impairment or loss, sensory or motor disturbance or dysphasia.

Presentation symptoms of SAH include:

■ Blood pressure elevation;

■ Tachycardia;

■ Retinal haemorrhage;

■ Papilledema;

■ Impaired neurologic function.

The factors that are generally used in prognostic include the severity of the haemorrhage, the degree of cerebral vasospasm or the occurrence of another bleeding episode.

Main diagnostic method is through vascular imaging and computed tomography determinations. These check for signs of aneurysmal cerebral bleeding and evaluate the amount of blood.

In order to prevent extravasation (blood traveling) into the subarachnoid space between the pial and arachnoid membranes, surgery is required. This prevents further impairment to the brain function and limits complication risk.

Other clinical assessment scales

There are other clinical tools that determine prognosis in subarachnoid haemorrhage, like the World Federation of Neurological Surgeons (WFNS) grading system and the Fischer scale, both with a classification system.

The WFNS scale is correlated with the number of points that are obtained by the patient in the neurological assessment provided by the Glasgow coma scale:

The Fisher scale is based on findings from computed tomography:

- Group 1 - No blood detected;

- Group 2 - Diffuse deposition of subarachnoid blood, no clots, and no layers of blood greater than 1 mm;

- Group 3 - Localized clots and/or vertical layers of blood 1 mm or greater in thickness;

- Group 4 - Diffuse or no subarachnoid blood, but intracerebral or intraventricular clots present.

Original source

Hunt WE, Hess RM. Surgical risk as related to time of intervention in the repair of intracranial aneurysms. J Neurosurg. 1968; 28(1):14-20.

Other references

1. Degen LA, Dorhout Mees SM, Algra A, Rinkel GJ. Interobserver variability of grading scales for aneurysmal subarachnoid hemorrhage. Stroke. 2011; 42(6):1546-9.

2. Rosen DS, Macdonald RL. Subarachnoid hemorrhage grading scales: a systematic review. Neurocrit Care. 2005; 2(2):110-8.

3. Weir RU, Marcellus ML, Do HM, Steinberg GK, Marks MP. Aneurysmal subarachnoid hemorrhage in patients with Hunt and Hess grade 4 or 5: treatment using the Guglielmi detachable coil system. AJNR Am J Neuroradiol. 2003; 24(4):585-90.