Cerebral cavernous malformation (CCM), also known as cavernous angioma, cavernous haemangioma, and cavernoma, is a vascular disorder of the central nervous system that may appear either sporadically or exhibit autosomal dominant inheritance. The incidence in the general population is between 0.1-0.5%, and clinical symptoms typically appear between 30 to 50 years of age. Once thought to be strictly congenital, these vascular lesions have been found to occur de novo.

This disease is characterized by grossly dilated blood vessels with a single layer of endothelium and an absence of neuronal tissue within the lesions. These thinly-walled vessels resemble sinusoidal cavities filled with stagnant blood. Blood vessels in patients with CCM can range from a few millimeters to several centimeters in diameter. CCM lesions commonly resemble raspberries in external structure.

Many patients live their whole life without knowing they have a cerebral cavernous malformation. Other patients can have severe symptoms like seizures, headaches, paralysis, bleeding in the brain (cerebral hemorrhage), and even death. The nature and severity severity of the symptoms depend on the lesion's location in the brain. Approximately 70% of these lesions occur in the supratentorial region of the brain; the remaining 30% occur in the infratentorial region.

Symptoms and Diagnosis

Clinical symptoms of this disease include recurrent headaches, focal neurological deficits, hemorrahagic stroke, and seizures, but CCM can also be asymptomatic. Diagnosis is most commonly made by magnetic resonance imaging MRI, but not all MRI exams are created equal. It's paramount that the patient request a gradient-echo MRI (aka T2-Flair) in order to unmask small or punctate lesions which may otherwise remain undetected. Sometimes quiescent CCMs can be revealed as incidental findings during MRI exams ordered for other reasons.

Sometimes the lesion appearance imaged by MRI remains inconclusive. Consequently neurosurgeons will order a cerebral angiogram or magnetic resonance angiogram (MRA). Since CCMs are low flow lesions (they are hooked into the venous side of the circulatory system), they will be angiographically occult (invisible). If a lesion is discernable via angiogram in the same location as in the MRI, then an arteriovenous malformation (AVM) becomes the primary concern.

CCMs & Venous Malformations

Many times a CCM is accompanied by a venous malformation (VM) which are also known as a developmental venous anomaly (DVA). These lesions appear either as enhancing linear blood vessels or caput medusae--a radial orientation of small vessels that resemble the hair of Medusa from Greek Mythology. These are normally benign lesions that provide normal brain drainage into the venous system. Conventional wisdom recommends leaving these lesions alone, even if surgical removal of the CCM is advocated.

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Classification of medullary venous malformations in the temporal lobe: According to location and drainage pathway
From Neurological Research, 7/1/02 by Ikezaki, Kiyonobu

Medullary venous malformation (MVM) is rare in the temporal lobe, and the radiologic characteristics of temporal MVM have not yet been clarified. In 12 previously reported cases with satisfactory angiographic or magnetic resonance information as well as two newly reported here, we analyzed the specific location and hemodynamics of temporal lobe MVMs, particularly with respect to venous drainage. Temporal lobe MVM typically were seen in the superior lateral portion of the temporal lobe near either the atrium or the inferior horn of the lateral ventricle. Venous drainage was classified into two main patterns: deep (three cases) and superficial (11 cases). Superficial drainage could be divided into two subtypes: lateral and anterior. Dilated deep medullary veins converged toward either the lateral wall of the atrium or the inferior horn of the lateral ventricle. In the deep-drainage type, medullary veins drained into subependymal veins such as the inferior ventricular vein and the lateral atrial vein, and then emptied into the basal vein of Rosenthal The anastomotic lateral mesencephalic vein was involved in one case as a variant of the basal vein. When the subependymal veins and/or the basal vein of Rosenthal or transverse sinus were hypoplasic, the medullary veins drained into either the Sylvian veins (anterior superficial type) or the vein of Labbe (lateral superficial type) through a characteristic large transcerebral vein. Drainage of temporal lobe MVM can be classified as deep, lateral superficial, or anterior superficial. [Neurol Res 2002; 24: 505-509] Keywords: Medullary venous malformation; temporal lobe; classification; venous angioma

INTRODUCTION

Intracranial medullary venous malformation (MVM) is a relatively common vascular abnormality that most often is a developmental anomaly of venous drainage in the periependymal zone1. Most supratentorial MVM are found in the frontal and parietal lobes1. MVM in the temporal lobe are relatively rare, and their specific anatomic locations and drainage pathways have not been well described. Among 18 reports of temporal lobe MVM, 12 included sufficient anatomic and angiographic information to analyze together with findings in two of our patients with temporal lobe MVM1-10. To evaluate the location and venous drainage pathways in our cases, we used magnetic resonance imaging (MRI) and three-dimensional computed tomography (3DCT) in addition to conventional angiography. We present these neuroradiologic findings in our cases and delineate three patterns of anatomic location and venous drainage into which temporal lobe MVM can be classified.

CASE PRESENTATION

Case 1

In a 33-year-old woman with a left frontal sinus pericranii that developed after head trauma in childhood, computed tomography with contrast medium disclosed a linear enhancing structure in the left temporal lobe (CT; Figure IA). By MRI, this linear lesion was hypointense in T1-weighted images and showed mixed signal intensity in T2-weighted images (1.5 Tesla; Signa, General Electric, USA; Figure 18). Gadolinium-diethylenetriaminopentaacetic acid (DTPA; 0.1 mmol kg^sup -1; Schering, Germany) -enhanced MRI including MR angiography revealed a brush-stroke pattern of many fine streaks in the lateral portion of the temporal lobe. These converged into a large linear stream that drained forward to the Sylvian vallecula (Figure 18). The venous phase of the conventional left carotid angiogram displayed a caput medusae appearance of dilated deep medullary veins converging toward the superolateral aspect of the atrium of the lateral ventricle (Figure 1C,D). Instead of draining into the subependymal veins, these veins were connected to several dilated central medullary veins that coursed anteriorly in the parenchyma of the temporal lobe to drain into the deep Sylvian veins where they were joined by the insular veins. The deep Sylvian veins finally drained into the cavernous sinus through the sphenoparietal sinus. The left internal cerebral vein drained into the MVM through subependymal veins such as the inferior ventricular vein and the lateral atrial vein. The left transverse sinus and the left vein of Labbe were not well developed. The left basal vein of Rosenthal was not visualized. The Galenic system was not visualized on the left, even though the internal cerebral vein, the basal vein, vein of Galen, and the straight sinus were all normally visualized on the right.

Case 2

In a 60-year-old woman, CT following head trauma incidentally disclosed left temporal MVM. Instead of conventional angiography, enhanced MR imaging and MR angiography by a three-dimensional time-of-flight method were carried out to evaluate the lesion. As in Case 1, the dilated deep medullary veins originated from the temporal subcortical area approximately 25 mm from the ventricular wall, and converged towards the superolateral wall of the inferior horn and the atrium of the lateral ventricle (Figure 2A,B). MR angiography and three-dimensional CT angiography showed dilation of subependymal veins such as the inferior ventricular veins and the lateral atrial veins (Figure 2CD). A large central medullary vein that collected drainage from these subependymal veins coursed anterolaterally to the cortical surface of the left temporal lobe and finally emptied into the sigmoid sinus through the vein of Labbe. The left transverse sinus and the left Sylvian veins were undeveloped, as also was true for the left basal vein of Rosenthal. The internal cerebral vein was visualized.

RESULTS

Reported MVMs in the temporal lobe with sufficient data for analysis (14, including our two cases) are listed in Table 1. Irrespective of the reported diagnosis, we excluded other cases from consideration because no angiographic demonstration was shown and detailed angiographic findings were not described.

Localization of MVM

The MVMs frequently were seen in the superolateral portion of the temporal lobe near either the atrium or the inferior horn of the lateral ventricle. Dilated medullary veins arose 10 to 25 mm from the atrium or the inferior horn of the lateral ventricle and converged toward the superolateral aspect of the ventricular wall.

Classification of drainage

Conventional angiography and MR angiography depicted two major types of drainage pathway, deep and superficial.

Deep drainage (three cases)

Dilated medullary veins drained into the subependymal veins and then emptied into the deep drainage system through the basal vein of Rosenthal. The anastomotic lateral mesencephalic vein took part in one case as a variant of the basal vein, draining into the superior petrosal sinus. Hypoplasia of the superficial cortical veins, the superficial Sylvian veins, and the vein of Labbe accompanied this deep-drainage type.

Superficial drainage (11 cases)

When the subependymal veins and/or the basal vein of Rosenthal were hypoplastic, the medullary veins drained superficially through the enlarged central medullary vein into either the Sylvian veins or the vein of Labbe after converging toward the superolateral wall of the lateral ventricle. This superficially draining group could be subdivided into two subtypes. In the anterior subtype (five cases), the vein of Labbe was underdeveloped and a transcerebral vein connected the lesion to the deep or superficial middle cerebral (Sylvian) veins, ultimately draining into the sphenoparietal or cavernous sinus. In the lateral subtype (six cases), the Sylvian veins or the inferior cerebral veins were poorly developed, and a transcerebral vein ran laterally to join the vein of Labbe, draining to the transverse-sigmoid sinus.

DISCUSSION

The incidence of temporal lobe MVM has been estimated as 1%-5% of intracranial MVM and 8%-- 10% of supratentorial MVM based on an extensive review of the literature1,4,11. The clinical significance of MVM remains controversial despite extensive discussion12-15. Major symptoms reported for supratentorial lesions include seizures and headache. Correlations between the symptoms and the lesion have been weak in most studies including our own. Approximately 38% of all patients had epilepsy, and 8% of them were found to have a focus related to the temporal lesion. Hemorrhage (15%) and either incidental or nonspecific (31%) presentation were somewhat less frequent in temporal lobe MVM than among all supratentorial MVM (31 % and 42%, respectively)4.

In frontoparietal MVM, abundant fine medullary veins (segment 1) usually course to the surface of the brain through large central medullary veins (segment 2), emptying into superficial cortical veins (segment 3)1. On rare occasions, medullary veins course to the superolateral margin of the lateral ventricle (longitudinal caudate veins of Schlessinger), and then join the lesion to the subependymal vein, emptying into the internal cerebral vein. The two-factor theory proposed by Huang et aLl for MVM, first proposed a compensatory mechanism for aplasia, hypoplasia, or thrombosis of connecting segments of the veins deep in the paraventricular areas; the alternative possibility proposed by these authors involves persistent fetal or embryonic vascular structures or reactivation of their remnants.

Subependymal veins play an important role in the venous drainage of the temporal lobe. These subependymal veins, such as the subependymal vein at the temporal tip, the inferior ventricular vein, and the lateral atrial vein, usually collect venous flow from the deep medullary veins in the temporal lobe near the inferior horn and the atrium of the lateral ventricle. For example, the inferior ventricular vein receives venous flow from the anterior wall of the atrium and the roof of the temporal horn, and the lateral atrial vein receives blood flow from the anterior and lateral wall of the atrium. These veins then join the second or third segment of the basal vein of Rosenthal.

Analysis of location and drainage in this study led to classification of temporal lobe MVM into three groups: those with lateral, superficial drainage; anterior, superficial drainage; and deep drainage (Figure 3).

Similar to drainage in supratentorial MVM9, the superficial type represents 75% of temporal lobe MVM. In frontoparietal MVM, the longitudinal caudate vein receives medullary veins coursing along the superolateral corner of the body of the lateral ventricle. Such a subependymal vein that corresponds to the longitudinal caudate vein is not present in the temporal lobe. Subependymal veins, such as the lateral atrial veins and the inferior ventricular veins may perform the same function as the longitudinal caudate vein, and an MVM can drain into the deep venous system through these subependymal veins, which would enlarge.

When the deep drainage system including subependymal veins, basal vein of Rosenthal, or transverse sinus is undeveloped, the area normally drained by these veins in the temporal lobe now drains superficially via dilated central medullary veins running along the lateral wall of the ventricle to empty into either Sylvian veins (anterior type) or the vein of Labbe (lateral type). When one of these veins is poorly developed, the large central medullary vein drains into the other (Figure 3).

Although our study clarified the neuroradiologic characteristics of temporal lobe MVM, the clinical significance of this classification should be clarified by study of larger numbers of temporal lobe MVM.

ACKNOWLEDGEMENTS

This investigation was supported by Grant (12671365) from the Ministry of Education, Japan. A part of this study was carried out at the Morphology Core, Graduate School of Medical Sciences, Kyushu University.

REFERENCES

1 Huang Y, Robbins A, Patel S, Chaudhary M. Cerebral venous malformations and a new classification of cerebral vascular malformations. In: Kapp JP, Schmidek HH, eds. The Cerebral Venous System and its Disorders, Orlando: Grune & Stratton, 1984: pp.373-503

2 Wilms G, Demaerel P, Marchal G, Baert A, Plets C. Gadoliniumenhanced MR imaging of cerebral venous angiomas with emphasis on their drainage. J Comput Assist Tomo 1991; 15: 199-206

3 Agnoli A, Hildebrandt G. Cerebral venous angiomas. Acta Neurochir 1985; 78: 4-12

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5 Ikeda K, Segawa F, Tomi H, Sunohara N, Onuma T. A case of temporal lobe epilepsy due to venous angioma: Detection by gadolinium-enhanced magnetic resonance imaging. J Jpn Epil Soc 1991; 9: 113-116 (Jpn, abstract in English)

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10 Yasargil Mg. Microneurosurgery IIIB: AVM of the Brain, Clinical Considerations, General and Special Operative Techniques, Surgical Results, Nonoperated Cases, Cavernous and Venous Angiomas, Neuroanesthesia, Stuttgart: George Thieme Verlag, 1987: pp. 405-418

11 Handa H, Moritake K. Venous angiomas of the brain. In: Fein JM, Flamm ES, eds. Cerebrovascular Surgery, New York: SpringerVerlag, 1985: pp. 1139-1149

12 Biller J, Toffol G, Shea J, Fine M, Azar KB. Cerebellar venous angiomas. A continuing controversy. Arch Neurol 1985; 42: 367-370

13 Lasjaunias P, Burrows P, Planet C. Developmental venous anomalies (DVA): The so-called venous angioma. Neurosurg Rev 1986; 9:233-242

14 Rothfus W, Albright A, Casey K, Latchaw R, Roppolo H. Cerebellar venous angioma: 'Benign' entity? AmJ Neuroradiol 1984; 5: 61-66 15 Saito Y, Kobayashi N. Cerebral venous angiomas: Clinical evaluation and possible etiology. Radiology 1981; 139: 87-94

Kiyonobu Ikezaki, Akira Nakamizo, Toshiyuki Amano, Takato Morioka, Takanori Inamura, Kiyotaka Fujii and Masashi Fukui

Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan

Correspondence and reprint requests to: Kiyonobu Ikezaki, MD, PhD, Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. [nobu@ns.med.kyushu-u.ac.jp] Accepted for publication March 2002.

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