Magnetic resonance imaging (MRI) in the diagnosis of cerebral arteriovenous angiomas

Transoral transclival removal of anteriorly placed cavernous malformations of the brainstem

BACKGROUND

The natural history of brain stem cavernous malformations is unfavorable because of their high hemorrhage rate and resulting neurological deterioration among patients. However, direct surgery of intrinsic and anteriorly situated cavernomas is hazardous and leads to a bad postoperative outcome because of trauma to lateral and dorsally situated eloquent areas of the brain stem.

METHODS

We review the cases of two patients with symptomatic cavernous malformations of the anterior brain stem and describe the usefulness of a transoral-transclival approach. A 23-year-old man developed progressive hemihypaesthesia and paraesthesia, hemiparesis with gait ataxia, dysarthria, dysphonia, and dysphagia. A 38-year-old woman suffered from an acute onset of vertigo with nausea and vomiting, diplopia, and paraesthesia of the left hand and foot. In both patients, computed tomography demonstrated the presence of brain stem hemorrhage, because of cavernous malformation. Magnetic resonance imaging showed a close proximity of the lesions to the pia mater only on the ventral surface of the brain stem.

RESULTS

In both patients, the cavernomas could be safely approached and completely resected via a transoral transclival route. Three months after surgery, neurological examination revealed marked neurological improvement. The 23-year-old patient showed slight gait ataxia, no hemiparesis, no cranial nerve palsies; the 38-year-old woman demonstrated no neurological symptoms except for minimal motor dysfunction of the left hand. In both cases, under perioperative prophylactic antibiotics, no meningitis was observed. The patients could subsequently return to their previous employment.

CONCLUSION

The transoral transclival approach for ventrally situated brain stem cavernomas allows a largely atraumatic resection of the lesion.

Factors predisposing to clinical disability in patients with cavernous malformations of the brain

The factors predisposing to an aggressive clinical course in cavernous malformations of the brain are not known. Disabilities from neurological deficits and from seizures were assessed and graded in 84 patients harboring 100 cavernous malformations and were correlated with patient sex and age, lesion size, lesion location, lesion multiplicity, and previous overt hemorrhage. Univariate analysis showed that female sex, infratentorial lesion location, and previous gross hemorrhage were significantly associated with subsequent neurological disability. Logistic regression analysis showed that infratentorial lesion location and previous gross hemorrhage were independent factors simultaneously and significantly associated with neurological disability. Age less than 40 was the only significant factor predisposing to seizure disability (in both univariate and multivariate analyses). Lesion size, multiplicity, and other factors did not influence clinical disability. This information should assist in management decisions regarding cavernous malformations.

Natural history of the cavernous angioma

The incidence and natural history of the cavernous angioma have remained unclear in part because of the difficulty of diagnosing and following this lesion prior to surgical excision. The introduction of magnetic resonance (MR) imaging has improved the sensitivity and specificity of diagnosing and following this vascular malformation. Seventy-six lesions with an MR appearance typical of a presumed cavernous angioma were discovered in 66 patients among 14,035 consecutive MR images performed at the Cleveland Clinic between 1984 and 1989. Follow-up studies in 86% of the cases over a mean period of 26 months provided 143 lesion-years of clinical survey of this condition. The most frequent presenting features were seizure, focal neurological deficit, and headache. While most lesions exhibited evidence of occult bleeding on MR imaging, there was overt hemorrhage in seven of the 57 symptomatic patients and only one overt hemorrhage occurred during the follow-up interval. The annualized bleeding rate was 0.7%. Analysis of the hemorrhage group revealed a significantly greater risk of overt hemorrhage in females. Pathological confirmation of cavernous angioma was obtained in all 14 surgical cases. This information assists in rational therapeutic planning and prognosis in patients with MR images showing lesions suggestive of cavernous angioma.

Comparison of magnetic resonance angiography, magnetic resonance imaging and conventional angiography in cerebral arteriovenous malformation

10 patients with an AVM of the brain were examined by magnetic resonance angiography (MRA), magnetic resonance imaging (MRI) and conventional cerebral angiography (CCA). From MRA in 7/10 patients important information about vascular supply could be provided; in 3 patients, all with small AVM's it could be only suspected. CCA revealed the vascularisation of the AVM's in all patients and showed additional hemodynamic aspects better than MRA. With MRI in all cases the AVM could be diagnosed, but only the involvement of the main cerebral vessels could be demonstrated: however, MRI is superior to MRA and CCA in showing the nidus and the involved brain structures.

Cerebral venous angiomas. MR imaging at 1.5 tesla

Sixteen cases of cerebral venous angiomas, seven cerebellar and nine supratentorial were imaged by magnetic resonance, using a T1 sequence and a motion compensated T2 sequence. The transcerebral draining vein of the lesion could be identified in thirteen out of sixteen patients. On T1-weighted images all the lesions were hypointense. On T2-weighted images, five lesions were hypointense, and eleven were hyperintense consistent with slow flow. In three cases the lesion was hemorrhagic. Three lesions with hypointense aspect on T1 and hyperintense aspect on T2-weighted images were only seen in retrospect, due to partial volume averaging in two and concomitant chronic hemorrhage in one. Before contrast, the peripheral dilated medullary veins could only be identified in five cases. On T2-weighted images, in three of these lesions the signal was higher than in the draining veins, pointing to a slower flow. After intravenous administration of Gadolinium, performed in twelve patients, the main transcerebral draining vein as well as the peripheral medullary veins could be well identified in all patients.

Cerebral vascular malformations: applications of magnetic resonance imaging to differential diagnosis

Twelve patients with cerebral vascular malformations (5 cavernous angiomas, 1 thrombosed arteriovenous malformation, and 6 venous angiomas) were studied with magnetic resonance (MR) imaging. All lesions were clearly depicted. Characteristic MR findings were obtained mainly on T2-weighted images: a markedly low intensity area was always seen. The margins of arteriovenous malformation (AVM) and venous angioma were irregular while those of cavernous angioma were smooth in all planes on T2-weighted images. Gradient-echo (GrE) pulse sequences were more sensitive than T2-weighted spin echo (SE) in lesion detection. MR imaging could play an important role in the differential diagnosis of cerebral vascular malformations.

"Nidus sparing sign" on computerized tomography in intracerebral haemorrhage due to a rupture of arteriovenous malformation

The authors investigated the validity of noncontrast computerized tomography (NCCT) to predict the presence of arteriovenous malformations (AVM) as a cause of intracerebral haemorrhage (ICH) in the acute stage. They found a small iso- or slightly hyperdense nodular or tubular defect devoid of haematoma in its periphery on NCCT in 8 of the 13 AVM cases that underwent both NCCT and contrast CT. This CT finding was named "nidus sparing sign" (NSS). This haematoma-free notch was enhanced on contrast infusion and confirmed to correspond to the AVM nidus surgically and pathologically. In one case with negative angiograms, a small AVM was verified histologically within the tissue corresponding to the NSS. The NSS noted on the NCCT could be of great value in case emergency surgery is needed for comatose patients with ICH, particularly lobar ICH, without enough time left to undergo angiography and/or magnetic resonance imaging. Neurosurgeons are able to safely perform an evacuation of the haematoma keeping in mind the possibility of a ruptured AVM and if so, the spatial relationship between the AVM nidus and the haematoma. This might also be a valuable CT sign in deciding whether or not angiography should be undertaken in ICH cases.

MRI diagnosis of vertebral arteriovenous malformations in neurofibromatosis

We describe two patients with neurofibromatosis, each of whom was found to have an arteriovenous malformation (AVM), an uncommon manifestation of the disease, presenting as an extradural space-occupying lesion in the cervical spine. In one patient the finding of an unsuspected AVM at operation led to massive blood loss; in the other magnetic resonance imaging (MRI) of the neck allowed the diagnosis to be made and the hazard of an operation to be avoided. Solid tumours that may occur in the disease of neurofibromatosis are known to cause neurological deficits as the result of space occupation. We wish to draw attention to another pathological entity which may cause neurological deficits: that of AVMs. We also propose that in the investigation of such a patient MRI be borne in mind as a non-invasive radiological tool, particularly as, hopefully, its cost reduces and its availability becomes more widespread.