Neuro--

Neuroradiology(1992) 34:57-61

radiology 9 Springer-Verlag1992

Cranial MRI and CT in patients with left atrial myxoma E. Hofmann:, T. Becket:, R. Romberg-Hahnioser 2, H. Reichmann2, M. Warmuth-Metz:, and M. Nadjmi: Departments of : Neuroradiologyand 2 Neurology,Universityof Wtirzburg,Josef-Schneider-StraBe11, W-8700Wtirzburg, Federal Republicof Germany Received:28 March 1991

Summary. Six of 12 patients with histologically verified left atrial myxoma showed CT and MRI evidence of ischemic lesions of varying size and location, predominantly in the left hemisphere. Key words: Cardiac myxoma - Stroke - Cerebrovascutar disease

Myxoma is the most common tumor of the heart and likely originates from the cardiac endothelium [1]. Myxomas are most common in patients 30-60 years of age, but can occur at any age [1, 2]. Sex distribution has been reported to range from equality to a 3:1 preponderance of women. Echocardiography provides a safe, noninvasive, highly accurate diagnosis [1]. Patients often manifest cardiac symptoms, nonspecific constitutional symptoms, and sequelae of cerebral or systemic embolization. Results of CNS embolization vary. Cerebral ischemia is most frequent and may be hemorrhagic [3, 4]. Embolic tumor mass may affect the arterial wall, increasing the risk of aneurysm [5, 6]. Primary intracranial hemorrhage is rare [7]. Myxoma emboli may proliferate and become symptomatic as systemic or cerebral metastases years after successful resection of the cardiac tumor [8]. Literature review often results in a bias towards overestimation of complicated or deleterious outcome of disease and spectacular neuroradiological/neuropathological findings. Cases reported in the literature may even be published more than once [3, 8, 9-15]. The present study was undertaken to describe the findings in a representative sample of patients which was compiled from internal medicine and thoracic surgery files.

Materials and methods A total of 12 patients in whom left atrial myxoma had been confirmed by surgery between 1981 and 1989 were included in the study. The postoperative period ranged from 2 months to 8 years.

Nine of the 12 patients gave their informed consent to undergo further neuroimaging studies: 5 by MRI, 3 by CT, and 1 by both CT and MRI. One patient with a preoperative CT died during the postoperative period due to heart failure. In 2 patients who only had clinical followup, perioperative CT or MRI studies were available. Cerebral angiography was not performed in any ,of the patients. MRI was performed on a 1.5 T Gyroscan S15 (Philips, Eindhoven, The Netherlands), using spin echo sequences (2100/30, 100/2 = TR/TE/excitations for spin density and T2-weighted images and 450/25/2 for Tl-weighted images). Patients with implanted ferromagnetic foreign bodies such as cardiac pacemakers or with claustrophobia underwent CT with contiguous 5-mm slices (GE 9800, General Electric, Milwaukee, Wis.). In all volunteers, CT and MRI were carried out without contrast medium. In the remaining patients, paramagnetic contrast medium was used for MRI in only 1 patient (case 1).

Results There were 11 women and i man. Average age was 51 years at initial myxoma manifestation and 56 years at the time of follow-up. Female sex and the middle age group predominated. Neurological symptoms comprised Parinaud syndrome due to a mesencephalic mass in 1 patient (case 1) and focal neurological deficits due to cerebral ischemia (aphasia, hemiparesis, hemianopia) in 5 patients (cases1-4,10). Imaging results are summarized in Table 1. In 5 patients, imaging studies showed no detectable abnormality. In i patient, a lesion was found in the left corona radiata. Clinical history and morphology suggested that this lesion represented periventricular leukomalacia from perinatal causes. Ischemic infarction was documented in 6 of the 12 patients (50 %). Nonspecific hyper-

58 1. N e u r o r a d i o l o g i c a l findings in 12 patients with left atrial myxoma Table

Case no.

1

2

Sex Age Initial clinical mani(years) festation Neuroradiologic examinations

Age Follwo-up study Neuroradiological examinations

F

CT and MRI: Lacunar infarct in left thalamus Suspected midbrain metastasis Slight ventricular enlargement Unspecific white matter lesions

40

CT: Left basal ganglia infarct

48

F

39

42

58

CT and MRI: Slight increase of ventricular dilatation Aqueducal stenosis Other findings unchanged (Fig. 5)

MRI: Pseudocystic old left basal ganglia infarct (Fig. 2) Left temporoparietaI gliosis MRI: Small infarcts in left cerebellar hemisphere Unspecific white matter lesions

3

F

50

CT: No abnormality detected

4

F

72

76 CT: Old left frontal infarct Left temporo-occipital watershed infarct

CT: Unchanged (Fig. 1)

5

F

48

Not performed

51

MRI: Lacunar right cerebellar infarct Unspecific white matter lesions (Fig. 3)

6

F

36

Not performed

44

7

F

49

CT and MRI: No abnormality detected

--

MRI: Lacunar infarcts in head of right caudate nucleus (Fig. 4) Unspecific white matter lesions Not performed

8

M

40

Not performed

61

CT: No abnormality detected

9

F

62

CT: No abnormality detected

--

10

F

54

CT: Periventricular leukomalacia (perinatal damage)

54

Not done (patient died due to cardiac failure immediately after surgery) CT and MRI (3 months after initial examination: unchanged)

11

F

6I

Not performed

65

12

F

57

CT:

--

CT: No abnormality detected Not performed

No abnormality detected

intense white matter lesions were also observed in 4 patients, all of whom had cerebral infarction. In I patient an ovoid mesencephalic lesion appeared hypodense on CT, hypointense on Tl-weighted MRI and hyperintense on both the proton density and the T2weighted SE sequences. Further study using T2-weighted gradient echo sequences showed loss of the aqueductal CSF pulsations indicating aqueductal compression and obstruction.

None of the patients showed CT or MRI evidence of intracranial aneurysm.

Discussion The female preponderance in the present study (11:1) exceeds the sex ratio of 1:1 to 3:1 reported in the literature

[1]. The average age in the present study was 51 years at the initial manifestation, in line with previous reports [2, 3].

Ischemia

According to literature reports, 10 %-45 % of all myxoma patients experience embolism to the CNS [1, 3, 14-17]. Neurological symptoms may be the only clinical manifestation of the tumor [18], making left atrial myxoma a treatable cause of stroke [10, 19]. One study of 42 young adults with cerebral infarction established left atrial myxoma to be the cause in 1 case (2.4 %). Another study considered myxoma to be the causative factor in 0.5 % of all acute cerebral ischemias [3, 20]. Cerebrovascular manifestations in left atrial myxoma are always the direct or indirect effect of embolism of tumorous material or of thrombus adherent to the myxoma mass [21]. Stenosis or occlusion of intracranial vessels by embolic material is considered the predominant cause of stroke in myxoma patients. In 42 cases sampled from the literature, 33 patients experienced cerebral ischemia [3-6, 9, 11, 14, 15, 19, 21-36]. The middle cerebral artery (MCA) territory was most frequently affected (left MCA 24, right MCA t0). The posterior cerebral artery was involved in 8 patients on the left and in 5 patients on the right. Anterior cerebral artery involvement was left-sided in 7 and right-sided in 5 patients. Infratentorial ischemia was noted in 6 patients. Again, literature reports emphasize a left-hemisphere preponderance. In the present series, cerebral ischemic lesions were documented in 6 out of 12 patients. Left-hemispheric location prevailed in 4 out of the 6 (Figs.l,2). The prevalence rate of cerebral ischemia is higher in our patients than in previous literature reports. Topographic distribution is summarized in Table 1. Hemorrhagic infarction is considered not to be uncommon [4, 12, 19, 32, 34]. Primary intracerebral hemorrhage has been reported by others [9, 22], but was not observed in the present series. Unusual cerebrovascular manifestations of atrial myxoma include the development of multi-infarct dementia due to recurring embolism [26], hemorrhage from a cerebral arteriovenous malformation probably due to tumor embolism [7], spinal artery embolism [37], and spreading of tumor cells to the superior sagittal sinus [34]. When the MRI studies from the present sample are considered and compared to the CTs, small lacunar infarctions (Figs. 3,4) probably would have passed unnoticed in previous CT examinations, as documented in case 3. Although it cannot be completely excluded that

59

Fig. 1. Case 4. Pseudocystic left frontal infarction (arrowheads). Left temporo-occipital watershed infarction (arrow). Minimal hypodense irregularities in the right frontal white matter Fig.2. Case 2. T2-weighted MRI. Encephalomalacic pseudocyst in the left basal ganglia region. Hypointense signal in the depth of the lesion represents hemosiderin deposits or iron in the shrunken corpus striatum (arrowhead)

lesions have occurred perioperativeiy, this eventuality seems unlikely: in those patients in whom the same imaging modality (CT or MRI) was chosen pre- and postoperatively, follow-up revealed no change in the findings. In patients with a preoperative CT scan and postoperative MRI no single, new lesion was encountered that could not be attributed merely to the increased sensitivity of MRI. There are few reports of MRI findings in left atrial myxoma [3, 22, 30, 35]. In 4 of the 6 cases reported, similar lacunar lesions are mentioned with some propensity to-

ward the medial thalamus. In the 2 remaining cases, anemic/hemorrhagic territorial infarcts are described. The hyperintense white matter lesions seen in 4 out of 7 patients examined by MRI are probably unrelated to the atrial myxomas. These 4 patients all had additional lacunar infarcts (Fig. 3). Such loci of increased white matter signal are strongly associated with cerebrovascular risk factors [38]. However, the increased prevalence of such lesions in our group (4/7 = 57 %) is not statistically different from the prevalence reported in age-matched asymptomatic subjects, considered to be 26-50 % [39].

Fig. 3 a,b. Case 5. a T2-weighted MRI. Small pseudocystic infarct in the right cerebellar hemisphere (arrowhead). b Proton density-weighted MRI. Nonspecific white matter lesions (arrowheads) Fig.4. Case 6. T2-weighted MRI. Lacunar infarcts in the head of the right caudate nucleus (arrowhead)

60

Fig.5 a--c. Case 1. a Proton density-weighted, b T2-weighted, c Tl-weighted MRI. Lesion in the midbrain, hyperintense in long TR series and hypointense in short TR series suggestingmyxoma metastasis (arrowheads). Lacunar infarcts in the left medial thalamus (arrows)

Aneurysm and metastasis Cerebral aneurysms have been considered a frequent neuroradiological finding in left atrial myxoma. In a sample of 42 literature cases, 16 (38 % ) showed fusiform outpouchings or saccular aneurysms [1, 4-7, 11, 16, 22, 28, 30, 31, 34, 40, 41]. Aneurysms were most frequently located in the MCA, with equal distribution in both hemispheres. They are typically multiple, measure only few millimeters in diameter and are to be found at peripheral vessel bifurcations distal to the circle of Willis [1, 40]. Resemblance to "mycotic" aneurysms has been emphasized [5]. It appears that aneurysms can both grow [6, 31] and decrease in size spontaneously [22]. In the present study, no aneurysm was visualized. This may be due to the lack of angiographic workup. Small aneurysms are not reliably identified by CT or MRI. On the other hand, Branch et al. [22] described an MRI finding of multiple aneurysms in a patient with left atrial myxoma. Michael et al. [4] reported that some aneurysms confirmed by angiography could be delineated by MRI amidst areas of hemorrhagic infarction. Aneurysms may result from implantation of metastatic emboli which infiltrate and disrupt the vessel wall [5]. Tumor and proliferating fibroblasts may replace large portions of the vessel wall. Subarachnoid hemorrhage is rare in myxoma patients [11]. There are patients in whom embolism preceded manifestation of a cerebral aneurysm with a good correspondence of the original vascular lesion and the location of the aneurysm [4, 6, 31]. On the other hand, aneurysms have been diagnosed without a clinical history of previous cerebral embolism [31]. In some cases, myxomatous tissue may extend to the adventitia of the vessel wall, thus resembling a tumor metastasis and conferring some aspects of a malignant tumor on myxoma [23]. Desousa et al. [8] and Frank et al. [42] first described such myxoma metastasis, and further reports have followed [23, 27, 41]. CT morphology of cerebral myxoma metastasis is variable. In the first case published, CT showed a hyperdense lesion with some contrast enhancement. On histological examination, a myxoma metastasis with extensive hemorrhage was

found [42]. A second metastatic lesion published also showed contrast enhancement. Histological workup revealed a tumor with large sinusoidal vessels surrounded by cuffs of myxomatous tissue [8]. A third case showed an enhancing osteolysis of the skull base [41]. In contrast, a fourth case of myxoma metastasis was hypodense on plain CT [27]. Irregular ring-like enhancement was reminiscent of glioblastoma or metastatic carcinoma. Histologically, myxomatous tissue with a high degree of cellularity was found. Polymorphic appearance of myxoma metastases reflects myxoma morphology: it ranges from an amorphous matrix with low cellularity to a richly vascularized stroma with a risk of hemorrhage from cavernous vessels [1, 32]. In the present series case 1 (Fig. 5) showed a mesencephalic lesion with no definite contrast enhancement. The pattern is compatible with myxomatous tissue and resembles the case reported by Kadota et al. [27]. The lesion has not enlarged during 3 years' follow-up. Cerebral metastases following myxoma removal are considered typical late complications which may become apparent even years after complete tumor resection [8, 41]. Once left atrial myxoma has been surgically removed, prognosis is considered favorable [3, 14,15]. In the present sample, prior imaging studies were available in 5 patients with the time interval ranging from a few months to 8 years. Comparison with follow-up studies failed to reveal new lesions. "New" abnormalities as shown by follow-up MRI were most likely attributable to the increased sensitivity of MRI. There are, however, literature reports of late neurological complications following even complete myxoma removal [11]. In conclusion, the pattern of neuroradiological findings in left atrial myxoma is characterized by cerebralischemic lesions with a wide range regarding size and extension, distribution and clinical relevance. Conspicuous neuroimaging findings were less frequent than might have been expected, judging from previous case reports and patient series. MRI allows the detection of small lacunar lesions which may be a characteristic sequel of left atrial myxoma.

61 T h e g o o d p r o g n o s i s a f t e r c o m p l e t e surgical r e m o v a l of c a r d i a c m y x o m a is u n d e r l i n e d b y t h e o b s e r v a t i o n t h a t in the f o l l o w - u p g r o u p no i n d i v i d u a l h a d lesions d e f i n i t e l y a t t r i b u t a b l e to t h e p o s t o p e r a t i v e p e r i o d . T h e risk of late c o m p l i c a t i o n s , t h o u g h small, s e e m s to w a r r a n t l o n g - t e r m clinical f o l l o w - u p e x a m i n a t i o n s .

Acknowledgements'. Professor Hacker, Herz- und Gef~i/3-Klinik, Bad Neustadt/Saale is acknowledged for patient referral and kind support. The authors also wish to thank Mrs. D. Bush for reviewing the manuscript.

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Department of Neuroradiology Josef-Schneider-Strage 11 W-8700 Wtirzburg Federal Republik of Germany