Central nervous system disorders

IV./4.4.: Additional diagnostics

IV./4.4.1.: Lumbar puncture

That cranial CT scan could be negative despite the typical complaints and neurological signs of subarachnoid hemorrhage - e.g. physical exercises prior the development of severe headache, meningeal sings etc. In this case, lumbar puncture is useful to establish the diagnosis; a negative result – no blood in the CSF – definitely exclude the subarachnoid bleeding.

Blood of the CSF could originate from subarachnoid bleeding or could be a result of a traumatic tap. To distinguish the subarachnoid blood from the traumatic bleeding – e.g. the blood got artificially to the CSF during the puncture – four fractions of a CSF sample should be taken. The bleeding is artificial if the CSF clears out from fraction 1 to 4. When the last fraction still tinted with blood, centrifugation is recommended and the supernatant should be examined. Yellow – xantochrom – supernatant is a sign of a subarachnoid bleeding older than 48 hours, while red – erythrochrom – supernatant is typical of a more recent hemorrhage.

IV./4.4.2.: Fundus examination / ophthalmoscopy

Patients with sudden onset, severe headache are often referred to a headache specialist or to an outpatient clinic. In these cases, a quick check of the fundus by an ophthalmoscope could be very informative. A subhyaloidal bleeding on the fundus – the blood is temporally located from the papilla - proves the diagnosis of subarachnoid hemorrhage even before the completion of a CT scan.

IV./4.4.3.: TCD – Transcranial Doppler

Change in the velocity of the blood flow in the circle of Willis is easily detectable with transcranial Doppler (TCD) method by an expert hand. Placing the transducer over the insonation windows of the skull - temporal (below the zygomatic arch), orbital (at the superior orbital fissure) or suboccipital (at the foramen magnum) window – we could measure the velocity of the blood flow in the middle cerebral artery, in the anterior cerebral artery or in the posterior cerebral / basilar artery, respectively. The normal velocity of the blood flow in the aforementioned arteries is 60, 50 and 40 cm/ sec.

Detection of the subarachnoid hemorrhage induced vasospasm, the non-invasive TCD measurement is more sensitive than the classic angiography. For example, a 30% reduction of diameter in the middle cerebral artery results less than 1 mm changes on an angiography image, while the TCD shows a twofold acceleration of the blood flow. In case of subarachnoid bleeding TCD measurement is recommended between 4 and 14 days of the illness. In summary, the velocity of blood flow beyond 120 cm/min in the circle of Willis refers to vasoconstriction. The rapid increase of the velocity is usually the sign of poor prognosis.