A patient with suspected subarachnoid haemorrhage presents with blood isolated in the fouh ventricle on a CT scan. Aneurysmal rupture is likely to have resulted from:
Answer is A (Posterior Inferior Cerebellar Aery Anurysm): 103. References with text Blood isolated to the fouh ventricle suggets a ruptued Posterior Inferior Cerebellar Aery (PICA) Aneurysm. The diagnosis is usually obvious on CT. Blood isolated to the fouh ventricle suggests a ruptured posterior inferior cerebellar aery anurysm' -- Plum & Posner's Diagnosis of Stupor & Coma (Oxford) 4th/145 `Subarachnoid Haemorrhage involving blood only from the fouh ventricle is almost diagnostic of Veebral aery -PICA aneurysm' -- Surgery of the Cranioveebral Junction (Thieme) 1998/323 `PICA aneurysm should be suspected when there is little blood in the cisterns supratentorially compared with the cisterna magna, around the brainstem and in the fouh ventricle' - Atlas of Neurosurgical Technique (Thieme) 2006/182 `Ruptured PICA aneurysm almost always coexist with intraventricular haemorrhage in the fouh ventricle and Hydrocephalus' -- Intracranial Malformation & Aneurysms (Springer) 2008/189 Posterior Inferior Cerebellar Aery Aneurysm Represents 1% to 3% of all intracranial aneurysm When a posterior inferior cerebellar aery (PICA) aneurysm ruptures, the patient may present with hemorrhage isolated to the posterior fossa and/or fouh ventricle; hemorrhage may extend to the cerebellum. Both PICAs need to be studied in all angiograms performed to rule out an intracranial aneurysm; this can be done by refluxing contrast into the contralateral veebral aery or by injecting each veebral aery individually. Conventional angiography fails to demonstrate an intracranial aneurysm in 5% of all patients with spontaneous subarachnoid hemorrhage. Most frequent presentation of PICA origin aneurysms Subarachnoid haemorrhage (SAH), and Intraventricular haemorrhage (4th ventricle), with Acute Hydrocephalus. (The cerebellum may be involved) PICA aneurysms lie in the close proximity to the fouh ventricle. Blood from the aneurysms enters the ventricular system (fouh ventricle) through either the foramen of Luschka or Magendie. Aneurysms and Vascular Malformations: Condition Comments Anterior communicating Approximately 30% to 35% of intracranial aneurysms. aery aneurysm Rupture results in hemorrhage in the gyrirecti, anterior interhemispheric fissure, septum pellucidum, and frontal horns of the lateral ventricles. Posterior communicating Approximately 30% to 35% of intracranial aneurysms. aery aneurysm Rupture tends to result in diffuse subarachnoid hemorrhage, but bleeding may be concentrated in the basilar cisterns. Middle cerebral aery Approximately 20% of intracranial aneurysms. bifurcation aneurysm Rupture results in hemorrhage in the syln fissure, frontal opercula and basilar cisterns. Basilar aery tip aneurysm Approximately 5% of intracranial aneurysms. Rupture results in hemorrhage in the basilar cisterns and posterior position of the third ventricle. Posterior inferior cerebellar Approximately 1% to 3% of intracranial aneurysms. aery aneurysm Rupture may produce hemorrhage isolated to the posterior fossa or fouh ventricle Post traumatic aneurysm Less than 1% of intracranial aneurysm. Common sites include the intracavernous poion of the internal carotid aery; the distal pa of the anterior cerebral aery; and distal branches of the middle cerebral aery. CT can predict aneurysm location based on the pattern of blood in -78% of cases (but mostly for MCA and A-comm aneurysms) ('Clinical Imaging: An Atlas of Differential Diagnosis' by Eisenberg (Lippincott Williams & Wilkins) 5th/1376) * Blood predominantly in anterior interhemispheric fissure (+- blood in lateral ventricles) or within the gyrus rectus suggests a-comm aneurysm * Blood predominantly in I syln fissure is compatible with p-comm or MCA aneurysm on that side * Blood predominantly in the prepontine or penduncular cistern suggets a basilar apex or SCA aneurysm. * Blood predominantly within ventricles: 1) Blood primarily in 4th and 3rd ventricle: suggests lower posterior fossa source, such as PICA aneurysm or VA dissection 2) Blood primarily in the 3rd ventricle suggets a basilar apex aneurysm
Posterior Inferior Cerebellar Aery Aneurysm
Anterior Communicating Aery Aneurysm
Posterior Communicating Aery Aneurysm
Basilar Aery Tip Aneurysm