Case 1
Excision of a pontine cavernous malformation via the floor of the fourth ventricle
A 28-year-old man presented with acute onset of vertigo, tinitus, and left limb and body numbness, together with unsteady gait. Physical examination revealed nystagmus, right VI and VII cranial nerve complete palsy (House-Brackmann grading 6/6), and left limb ataxia and deceased sensation. Imaging showed a pontine hematoma.
Axial CT scan of pontine cavernous malformation:
Sagittal CT scan of pontine cavernous malformation:
T1-weighted axial MRI of pontine cavernous malformation:
T1-weighted sagittal MRIs of pontine cavernous malformation:
Surgical excision of the lesion was indicated because the patient was symptomatic with disabling neurological deficit due to hemorrhage of the cavernous malformation and the hematoma was shown to reach the surface of the floor of the fourth ventricle on T1-weighted MRI sequence. This suggested that it was feasible to reaching the lesion surgically with minimal damage to the brainstem. A posterior fossa craniotomy was performed for evacuation of the pontine hematoma through the floor of the fourth ventricle.
Operative setup: Shown are wires of electrodes placed for monitoring of cranial nerves VII, VIII, IX, X, and XII during surgery.
Positioning for surgery: Shown is the patient in prone position with marking for a midline suboccipital craniotomy. Maximal flexion of the neck was required to facilitate visualization of the floor of the fourth ventricle.
Exposure of the ventricle floor: Seen is the inferior part of the IV ventricle between the tonsils and the vermis. A telovelar approach was used in which the cerebellomedullary fissure was split on both sides to minimize retraction to the vermis to expose the floor of the IV ventricle.
Dorsal surface of hematoma: : The hematoma was pointing (blue arrow)just above striae modulars. The facial colliculi, though distorted, were nearby on both sides of the midline. The facial nerve was mapped with electrical stimulation before entering the floor to resect the lesion.
Cavernous malformation of the brain: Brownish abnormal tissue (blue arrow) typical of a cavernous malformation was removed with microbiopsy forceps (yellow arrow).
Postoperative axial CT scan: This scan was done soon after surgery.
The patient was significantly improved 3 months postoperatively. He walked unaided. His facial palsy was mild (House-Brackmann grading 2/6). Pathological examination confirmed the diagnosis of cavernous malformation.
Case 2
Excision of potinomedullary junction cavernous malformation via a retromastoid approach
On MRI for investigation of a parotic cyst, this 14-year-old boy was found to have multiple brain lesions consistent with cavernous malformations.
T2-weighted axial MRI of a cavernous malformation: Scan shows a small hyperintense lesion with a hypointense rim (red arrow) in the left side of the pons
Gadolinium-enhanced T1-weighted coronal MRI of cavernous malformation: Image shows a hyperintense lesion with hypointense rim (red arrow) in the left temporal lobe.
The patient had acute onset of severe headache associated with double vision and right-sided numbness for one day in one year after his initial presentation. Physical examination revealed left VI cranial nerve palsy. CT of the brain showed multiple small lesions.
CT scan of multiple cavernous malformations: The one in the left side of the pons (red arrow) suggested the pre-existing lesion developed acute overt hematoma. It was consistent with the patient’s symptoms of focal neurological deficit.
His MRI showed evidence of recent hematoma of the left pontine lesion (red arrows).
T1-weighted axial MRI of a cavernous malformation: Red arrow points to a left pontine cavernous malformation.
T2-weighted axial MRI of a cavernous malformation: Red arrow points to a left pontine cavernous malformation.
SWI axial MRI of a cavernous malformation: Red arrow points to a left pontine cavernous malformation.
MRA showed no evidence of AVM. The diagnosis was cavernous malformation with bleeding of the pontine lesion. The patient was treated conservatively because the lesion did not reach the surface of the brainstem. His symptoms completely abated in 6 months. MRI 3 years later showed that the pontine lesion had decreased in size. However, 1 year later he developed sudden onset severe headache with double vision and right-sided weakness and numbness Physical examination revealed VI cranial nerve palsy, right hemparesis, and decreased sensory function. The symptoms progressed by the next day with decreased consciousness.
Axial CT scan of a cavernous malformation: The scan was done on day one of hemorrhage (arrow).
Axial T2-weighted MRI of a cavernous malformation:
GRE sagittal MRI of a cavernous malformation: Shown is the blooming artifact of the hematoma.
T1coronal MRI of cavernous malformation: The image suggests that the lesion reached the surface of the brainstem.
At this stage, surgical excision of the lesion was indicated in view of recurrent symptomatic hemorrhage with impaired consciousness, and the fact that the lesion reached the surface of the brainstem. Emergency surgery for evacuation of the hematoma and excision of the lesion was performed via a left retromastoid approach.
Surgical view of cavernous malformation in the pons: The lesion (red arrow) is seen behind the lower cranial nerves (yellow arrows) in the lateral wall of the pons.
Surgical view of exposed cavernous malformation: A corridor has been established to the lesion (red arrow).
Surgical view after excision of the cavernous malformation: The cranial nerves IX and X (yellow arrow) and VII and VIII (blue arrow) were intact.
Pathological examination confirmed the diagnosis of cavernous malformation. On clinical follow-up 6 months postoperatively, the patient reported that he had returned to school and had only mild right-sided weakness and decreased in sensation.
Case 3
Excision of midbrain cavernous malformation via a subtemporal approach
A 12-year-old boy presented with insidious onset of a progressive left-sided weakness for 1 year. Physical examination revealed left-limb hemiparesis with upper motor neuron signs. On CT and MRI/MRA, there was a large lesion (red arrow) in the midbrain without evidence of AVM.
Axial CT scan of a cavernous malformation: The lesion is seen in the was left anterolateral midbrain at the level of the uncus of the temporal lobe. It suggested that the lesion was at and above the level of the tentorium.
The lesion is seen in the was left anterolateral midbrain at the level of the uncus of the temporal lobe. It suggested that the: The scan shows the cavernoma in the right cerebral peduncle.
T1-weighted sagittal MRI of a cavernous malformation: The red arrow points to the superior pole of the lesion.
T1-weighted sagittal gadolinium enhanced MRI of a cavernous malformation: Contrast enhancement suggested that the lesion could be quite vascular, and this was confirmed during surgery.
Positioning of patient: Shown is the planned incision for a subtemporal approach.
The lesion was totally excised. Intraoperative monitoring of the cranial nerves was used. Cranial nerve IV was identified and preserved. Because the lesion was highly vascular, circumferential excision was used. Postoperatively the patient had partial palsy of cranial nerves II and IV, which resolved in 6 months. Pathological examination of the lesion confirmed that it was a cavernous malformation.
T1-weighted axial MRI:
T1-weighted gadolinium-enhanced axial MRI: There was some contrast enhancement in the operated site that had no interval change in several MRIs over a 10-year period.
T2-weighted axial MRI:
Residual hemosiderin is seen on the T2-weighted image. This is not uncommon when resecting a cavernnoma in a critical area where radical resection, including the perilesional hemosiderin-laden tissue, is not possible. In noneloquent areas and for patients with epilepsy, resection of the hemosiderin-laden tissue should be the goal.
Case 4
Excision of a mesencephalic cavernous malformation via the third ventricle
A 30-year-old man presented with sudden onset of diplopia.
Axial CT at presentation: This unenhanced CT scan of the brain shows a focal hematoma in the midbrain.
T1-weighted axial MRI: This scan shows the hematoma in the left cerebral peduncle. It reached the brainstem surface.
GRE axial MRI of hematoma: Shown is the blooming artefact of the hematoma.
T1-weighted gadolinium-enhanced coronal MRI: A possible associated venous anomaly may be seen on the inferior border.
A cavernous malformation was the leading differential diagnostic possibility. Although the patient was symptomatic with neurological deficit and the lesion reached the surface of the brainstem in the anterior medial aspect of the cerebral peduncle, surgical excision was not contemplated because entry through the interpeduncular region had a high chance of damaging cranial nerve III. The patient was treated conservatively, and MRI was repeated several months later.
T2-weighted axial MRI of a cavernous malformation: The typical appearance of a cavernous malformation (red arrow) is now apparent at the former hematoma site in the left cerebral peduncle.
T1-weighted axial MRI of a cavernous malformation: In comparison with the previous MRI, the hemorrhage had become smaller and was away from the brainstem surface.
T1-weighted gadolinium-enhanced axial MRI: In addition to the cavernoma, an associated developmental venous anomaly is seen (green arrow).
The features were compatible with the diagnosis of cavernous malformation. Clinically, the patient’s diplopia had largely subsided with subtle residual left ptosis. However, he developed progressive left ptosis 1 year later Physical examination showed left ophthalmoplegia with fixed dilated pupils and ptosis. After he was admitted to the hospital, his condition deteriorated further to bilateral ophthalmoplegia, right-limb weakness, and impaired consciousness, which required ICU admission and tracheal intubation.
Axial CT scan at admission: The scan shows a hematoma in the upper brainstem with obstructive hydrocephalus.
The patient underwent surgery for evacuation of the hematoma and excision of the cavernous malformation via a frontal interhemispheric transfornicial approach.
Sagittal CT scan of pontine cavernous malformation: The arrow shows the planned surgical trajectory.
Intraoperative view of the floor of the third ventricle: The upper part of the brainstem was seen bulging into the third ventricle. The underlying hematoma was close to rupturing into the ventricle (red arrow).
Intraoperative view of the resection cavity:: After evacuation of the hematoma and excision of the lesion, the brainstem was significantly decompressed.
Postoperative T1-weighted coronal MRI: No residual lesion is demonstrated.
Postoperative T1-weighted axial MRI: Focal hypointensity indicates the previous location of the lesion.
Postoperative gadolinium-enhanced T1-weighted axial MRI: No enhanced lesion is demonstrated.
Postoperative T2-weighted axial MRI: Postoperative T2-weighted axial MRI
Postoperative GRE axial MRI: Mild focal hyperintensity (red arrow) around the surgical site identified by GRE sequence represents a small amount of hemosiderin.
Pathological examination confirmed that the lesion was a cavernous malformation. The patient gradually recovered with residual left cranial nerve III palsy. . He returned to work as a bank clerk. There was no clinical or imaging evidence of further hemorrhage.
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