Angiographic Appearance of a Papilloma of the Choroid Plexus

[Microsurgical anatomy of the anterior choroidal artery]

Microdissection of 100 hemispheres from human cadavers were performed in order to study the anatomic characteristics of the anterior choroidal artery (AChA). One AChA per hemisphere was found. In 98% of hemispheres the AChA arose from the internal carotid artery (ACI) 2.4mm distal to the origin of the posterior communicating artery (ACoP) and 4.7mm proximal to the carotid bifurcation. One or more perforating branches arose from communicating segment of ACI in 29% of hemispheres. The average calibre of the cisternal portion was 0.9mm and the plexal portion 0.7mm. The most frequent branches of the cisternal portion pass to the optic tract, cerebral peduncle, uncus and lateral geniculate body. Anastomosis were found between branches of the AChA and posterior cerebral artery, ACoP, middle cerebral artery and ACI. The results are discussed.

Microsurgical anatomy of the choroidal arteries: lateral and third ventricles

✓ The microsurgical anatomy of the arteries supplying the choroid plexus of the lateral and third ventricles was examined in 50 formalin-fixed cerebral hemispheres using × 3 to × 20 magnification. There was marked variation in the area of choroid plexus supplied by the choroidal arteries; however, the most common pattern was for the anterior choroidal artery (AChA) to supply a portion of the choroid plexus in the inferior horn and part of the atrium; the lateral posterior choroidal artery (LPChA) to supply a portion of the choroid plexus in the atrium and posterior part of the temporal horn and body; and the medial posterior choroidal artery (MPChA) to supply the choroid plexus in the roof of the third ventricle and a portion of that in the body of the lateral ventricle. The LPChA's and MPChA's occasionally sent branches to the choroid plexus on the contralateral side. The most frequent neural branches of the three choroidal arteries were as follows: AChA branches to the optic tract, cerebral peduncle, temporal lobe, and lateral geniculate body; LPChA branches to the thalamus, geniculate bodies, fornix, and cerebral peduncles; and MPChA branches to the thalamus, pineal body, cerebral peduncle, and tegmentum of the midbrain. Each of the choroidal arteries was divided into a cisternal and plexal segment. The cisternal segments were the most common site of origin of neural branches, but they also gave rise to some plexal branches. The plexal segments occasionally gave rise to neural branches.

Microsurgical anatomy of the posterior cerebral artery

✓ In order to define the microsurgical anatomy, 50 posterior cerebral arteries (PCA's) were examined using × 3 to × 40 magnification. The PC A was divided into four segments: Pt was the segment proximal to the posterior communicating artery (PCoA); P2 extended from the PCoA to the posterior margin of the midbrain and was subdivided into an equal anterior (P2A) and posterior (P2P) half; P3 began at the posterior midbrain, ran within the quadrigeminal cistern, and ended at the anterior limit of the calcarine fissure. The PCA had three types of branches: 1) cortical branches to the cerebrum; 2) central branches to the brain stem; and 3) ventricular branches to the choroid plexus. The largest branches reaching the lateral surface of the cerebrum were located immediately anterior to the preoccipital notch, and in most cases were branches of the posterior temporal artery. This area offers a greater than 75% chance of finding a vessel large enough to perform a microvascular anastomosis. The central branches were of two types: 1) direct perforating, and 2) circumferential. The direct perforating branches arising on P1 were the posterior thalamoperforating arteries. The “thalamogeniculate artery,” the vessel said to be occluded in the “thalamic syndrome,” was also of the direct perforating type, but it was a series of small arteries arising from P2A and P2P rather than being a single vessel. The circumferential arteries usually arose from P1 and encircled the midbrain providing branches as far posteriorly as the colliculi. The branches to the choroid plexus were the medial and lateral posterior choroidal arteries; the former usually arose from P2A and entered the roof of the third ventricle, and the latter arose as a series of arteries from P2P and passed over the pulvinar to enter the lateral ventricle.

Choroidal arteries in the diagnosis of thalamic tumors

✓ Arteriograms of 12 patients with space-occupying lesions involving the thalamus were compared with 100 vertebral and carotid arteriograms reported as normal. It was found that masses that involve the thalamus primarily or secondarily affect the choroidal arteries in a characteristic manner. The most commonly involved vessel is the lateral posterior choroidal artery. The medial posterior choroidal artery may also be affected because of its contribution to the dorsal medial nucleus of the thalamus and its occasional course around the pulvinar. Because the anterior choroidal artery is reciprocal in size to the lateral posterior choroidal artery, the lesion will often be demonstrated on carotid angiography.

Diagnóstico angiográfico dos tumores de plexo coróide do ventrículo lateral

Os autores consideram a angiografia cerebral como método de escolha para o diagnóstico dos tumores de plexo coróide dos ventrículos laterais. As pneumografias, por necessitarem de grande quantidade de contraste, são muito traumatizantes e, não raro, insuficientes. Nos 5 casos apresentados, as angiografias cerebrais demonstraram a existência de circulação patológica, permitindo o diagnóstico correto. Outro elemento interessante é a demonstração da dilatação do côrno temporal bloqueado. Além disso, o exame permite estudar os vasos aferentes e eferentes, facilitando, desta maneira, a tática cirúrgica. O aspecto angiográfico de um caso de carcinoma foi diverso dos 4 casos de papiloma.