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Edward H. Oldfield, Andrew Bennett III, Michael Y. Chen and John L. Doppman

✓ Spinal dural arteriovenous fistulas (AVFs) frequently cause progressive myelopathy. When they are localized by imaging studies, surgery can be safely performed by simply interrupting the vein draining the fistula intradurally, and the results will be excellent and lasting. In some patients with clinical features of a spinal dural AVF and in whom magnetic resonance imaging and/or myelography findings are consistent with a diagnosis of a spinal dural AVF, however, spinal arteriography demonstrates no such results. The authors used a simple strategy based on knowledge of the epidemiology, pathophysiology, and anatomy of spinal dural AVFs to manage these cases successfully. In two patients, atherosclerotic occlusion was the primary cause for the failure of arteriography to visualize the dural AVF. The presence of an aortic aneurysm was an additional contributing factor preventing arteriographic visualization in one of these patients. In a third patient, massive obesity, and aortic atheroslerosis and tortuosity contributed to the absence of findings on three spinal arteriograms before surgical exploration lead to a more focused arteriographic examination that was successful.

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Joe C. Watson, Thomas H. Shawker, Lynnette K. Nieman, Hetty L. DeVroom, John L. Doppman and Edward H. Oldfield

Object. Pituitary surgery has been reported to produce remission of Cushing's disease with preservation of pituitary function in only 60 to 70% of patients. The inability to identify an adenoma accounts for most failed sellar explorations. Most negative surgical explorations occur in patients in whom magnetic resonance (MR) imaging of the pituitary demonstrates normal findings, which happens in at least 35 to 45% of patients with Cushing's disease.

Methods. To examine the usefulness of intraoperative ultrasonography (IOUS) for identifying an adenoma in patients with no demonstrable tumor (negative findings) on pituitary MR imaging, we prospectively assessed the results of IOUS in 68 patients with a negative (59 patients) or equivocal (nine patients) MR image from a consecutive series of 107 patients with Cushing's disease (64%). We compared surgical findings and outcomes in these 68 patients with a group of 68 patients with Cushing's disease and negative findings on MR imaging in whom IOUS was not available.

Intraoperative ultrasonography localized a tumor in 47 (69%) of 68 patients with negative findings on MR imaging. Surprisingly, the size of the adenomas that were detected with IOUS compared with the size of those not detected did not differ (6.8 ± 3.4 mm compared with 6.1 ± 2.8 mm [mean ± standard deviation], respectively [p = 0.5]). In four patients, no adenoma was found at surgery or in the pathological specimen (“true negative”). In eight patients, nine abnormalities detected by IOUS that were suspected adenomas were negative on exploration (“false positive”). Thus, IOUS has a sensitivity of 73% and a positive predictive value of 84% for detecting pituitary adenomas in patients with Cushing's disease and negative findings on MR imaging. Compared with the 68 patients who did not undergo IOUS, remission after surgery was improved (61 patients [90%] compared with 57 patients [84%]), the number of tumors found on exploration was increased (61 tumors compared with 51 tumors; p = 0.02), and the number of hemihypophysectomies was decreased (five compared with 15; p = 0.02) with IOUS. When the groups were compared after excluding patients with prior pituitary surgery, tumors were found in 91% versus 72% (p = 0.008), and remission occurred in 95% versus 87% of patients, respectively, in the groups that had or did not have IOUS.

Conclusions. The IOUS is a sensitive imaging modality when used in patients with Cushing's disease in whom findings on pituitary MR imaging are negative. The improved ability to detect and localize these tumors by using IOUS positively affects surgical outcome.

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R. Bryan Mason, Lynnette K. Nieman, John L. Doppman and Edward H. Oldfield

✓ When the surgeon identifies an adenoma within the gland and selectively excises it, endocrine-active pituitary tumors are usually cured and pituitary function is preserved. Occasionally ectopic adenomas arise primarily in the pituitary stalk or arise superiorly in the midportion of the anterior lobe and extend upward within the stalk. To determine if these tumors can be selectively excised with preservation of pituitary function, the authors examined the outcome of selective adenomectomy in 10 patients with Cushing's disease with an ectopic adenoma originating in, and confined to, the stalk (four microadenomas) or an adenoma extending superiorly through the diaphragma sella and into the stalk (five microadenomas and one macroadenoma) from an operative series of 516 patients with Cushing's disease.

To reach the adenoma transsphenoidally in these patients, the diaphragma sella was incised anteroposteriorly in the midline to the anterior edge of the stalk, the suprasellar cistern was entered, and the adenoma was selectively excised using care to limit injury to the infundibulum. After selective adenomectomy, Cushing's disease remitted in all patients. All patients were hypocortisolemic immediately after surgery and required hydrocortisone for up to 21 months. Apart from the adrenal axis, pituitary function was normal in five patients in the immediate postoperative period, including two patients with tumors confined to the stalk and three patients with preoperative hypothyroidism (one patient) and/or hypogonadism (three patients). Three others with transient postoperative hypothyroidism (one patient) or diabetes insipidus (two patients) had normal pituitary function within 7 months of surgery. One patient with hypothyroidism and one with hypogonadism before surgery had panhypopituitarism postoperatively. A patient with a microadenoma located high in the stalk next to the optic chiasm had bitemporal hemianopsia postoperatively.

These results demonstrate the feasibility of achieving curative transsphenoidal resection and preservation of pituitary function in cases of pituitary adenomas that are confined to the pituitary stalk or tumors that extend superiorly within the stalk from an intrasellar origin.

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R. Bryan Mason, Lynnette K. Nieman, John L. Doppman and Edward H. Oldfield

When the surgeon identifies an adenoma within the gland and selectively excises it, endocrine-active pituitary tumors are usually cured and pituitary function is preserved. Occasionally ectopic adenomas arise primarily in the pituitary stalk or arise superiorly in the midportion of the anterior lobe and extend upward within the stalk. To determine if these tumors can be selectively excised with preservation of pituitary function, the authors examined the outcome of selective adenomectomy in 10 patients with Cushing's disease with an ectopic adenoma originating in, and confined to, the stalk (four microadenomas) or an adenoma extending superiorly through the diaphragma sella and into the stalk (five microadenomas and one macroadenoma) from an operative series of 516 patients with Cushing's disease.

To reach the adenoma transsphenoidally in these patients, the diaphragma sella was incised anteroposteriorly in the midline to the anterior edge of the stalk, the suprasellar cistern was entered, and the adenoma was selectively excised using care to limit injury to the infundibulum. After selective adenomectomy, Cushing's disease remitted in all patients. All patients were hypocortisolemic immediately after surgery and required hydrocortisone for up to 21 months. Apart from the adrenal axis, pituitary function was normal in five patients in the immediate postoperative period, including two patients with tumors confined to the stalk and three patients with preoperative hypothyroidism (one patient) and/or hypogonadism (three patients). Three others with transient postoperative hypothyroidism (one patient) or diabetes insipidus (two patients) had normal pituitary function within 7 months of surgery. One patient with hypothyroidism and one with hypogonadism before surgery had panhypopituitarism postoperatively. A patient with a microadenoma located high in the stalk next to the optic chiasm had bitemporal hemianopsia postoperatively.

These results demonstrate the feasibility of achieving curative transsphenoidal resection and preservation of pituitary function in cases of pituitary adenomas that are confined to the pituitary stalk or tumors that extend superiorly within the stalk from an intrasellar origin.

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Ian E. McCutcheon, John L. Doppman and Edward H. Oldfield

✓ Although most vascular abnormalities of the spinal cord are now ascribed to an abnormal communication between a dural artery and a medullary vein on the dura near a sensory nerve root, these lesions are too small for their anatomy to be demonstrated directly by spinal arteriography. Thus, it is unknown whether the site of dural arteriovenous shunting is an arteriovenous malformation (AVM), implying a congenital origin, or is a direct arteriovenous fistula (AVF), implying an acquired etiology.

The authors treated six patients by en bloc resection of the involved dural root sleeve, proximal nerve root, and adjacent spinal dura. All of the patients presented with myelopathy and their arteriograms were consistent with a spinal dural vascular malformation. The lesions occurred between T-6 and T-12, levels at which clinical deficits from such resection are minimal. The dural artery or medullary vein associated with the vascular malformation was cannulated and a dilute solution of barium sulfate was injected during sequential fine-grain radiography. In all of the lesions the artery split into daughter vessels that coalesced one to three times to form a skein of arterial loops in the dura that invariably emptied into a medullary vein without an intervening capillary plexus. Several medium-to-small collateral vessels arising from adjacent intercostal or lumbar arteries were commonly present in the dura and converged at the site of the AVF to join a single medullary vein.

These results show that spinal dural AVMs are direct AVFs that link the dural branch of the radiculo-medullarydural artery with the intradural medullary vein. They also provide an anatomical explanation for the presence of a multiple segmental arterial supply and a single draining medullary vein of spinal dural AVFs, and the propensity for reestablishment of flow through the arteriovenous shunt after embolic occlusion.

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Zvi Ram, Thomas H. Shawker, Mary H. Bradford, John L. Doppman and Edward H. Oldfield

✓ Microadenomas of the pituitary vary in size, particularly those related to Cushing's disease. They are often not visualized on preoperative magnetic resonance (MR) imaging and may be difficult to find during surgical exploration of the pituitary. To enhance intraoperative localization of pituitary adenomas, we assessed the feasibility of using ultrasound to detect and localize pituitary tumors. Intraoperative ultrasound (IS) in the axial and sagittal planes was performed with an Intrascan system using a 12-MHz mechanically oscillating, end-firing transducer. Interpretation of the scans was performed by two individuals, who were usually blinded to the results of preoperative MR imaging or petrosal sinus sampling.

Twenty-eight patients were examined. Eighteen of these patients had microadenomas (1.5–7 mm), all with Cushing's disease; nine had macroadenomas (10–20 mm), three of which were adrenocorticotropic hormone—secreting, three growth hormone—secreting, two thyroid-stimulating hormone—secreting, and one nonfunctioning; and one patient had an intrasellar craniopharyngioma. Normal sellar and parasellar structures, such as intrapituitary cysts, the intracavernous carotid arteries, and the diaphragma sella were easily visualized. Twenty-three of the 28 tumors, including 13 of the 18 microadenomas, were detected on IS (82% sensitivity). Tumors were seen as hyperechoic masses in 19 patients, mixed echogenicity in three, and isoechoic in one. In most macroadenomas IS allowed visualization of the interface between the tumor and the normal pituitary gland. These results indicate the potential of IS to aid the intraoperative localization and definition of pituitary tumors.

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John K. B. Afshar, John L. Doppman and Edward H. Oldfield

✓ To establish if interruption of the intradural draining spinal vein or surgical excision are curative treatments for spinal dural arteriovenous fistulas (AVFs), the medical records and radiographic studies of 19 patients with spinal dural AVFs and progressive myelopathy were reviewed. Spinal arteriograms were obtained before and within 2 weeks after surgery in 19 patients, and after a delay of 4 months or more in 11 patients. The mean clinical and arteriographic follow up was at 37 and 35 months, respectively. In the 11 patients who underwent excision of the dural AVF there was no evidence of a residual lesion upon immediate or delayed postoperative arteriography. Surgery in eight patients consisted of simple interruption of the intradural draining vein as it entered the subarachnoid space. In six of these patients the vein draining the AVF intrathecally provided the only venous drainage of the AVF. In these six patients there was no immediate (six of six) or delayed (four of six) arteriographic evidence of residual or recurrent flow through the AVF. Two patients had an AVF with both intra- and extradural venous drainage; after intradural division of the draining vein there was residual flow through the AVF into the extradural venous system. In one of these two patients intrathecal venous drainage was reestablished, which required additional therapy. In the other patient the extradural AVF spontaneously thrombosed and was not evident on delayed follow-up arteriography.

In patients with spinal dural AVFs with only intrathecal medullary venous drainage, which includes most patients with these lesions, surgical interruption of the intradural draining vein provides lasting and curative treatment. In patients with both intra- and extradural drainage of the AVF, complete excision of the fistula or interruption of the intra- and extradural venous drainage of the fistula is indicated. In patients in whom a common vessel supplies the spinal cord and the dural AVF, simple surgical interruption of the vein draining the AVF is the treatment of choice, as it provides lasting obliteration of the fistula and it is the only treatment that does not risk arterial occlusion and cord infarction. Simple interruption of the venous drainage of a spinal dural AVF provides lasting occlusion of the fistula, as it does for cranial dural AVFs, if all pathways of venous drainage are interrupted. This result provides further evidence that the venous approach to the treatment of dural AVFs can be used successfully.

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B. Gregory Thompson, John L. Doppman and Edward H. Oldfield

✓ Cranial dural arteriovenous fistulae (AVF's) of the tentorial incisura or the dura of the middle fossa have a much higher incidence of draining via leptomeningeal veins than do AVF's of the transverse-sigmoid sinuses or the cavernous sinus. Such a drainage pattern is associated with an increased incidence of intracranial hemorrhage and progressive focal neurological deficits. Patients with cranial dural AVF's often undergo surgical excision and/or endovascular embolization for elimination of the AVF. Since these lesions are frequently large and involve the skull base or adjacent dural sinuses, extensive surgery is often required. In contrast, spinal dural AVF's with only intradural venous drainage to the medullary venous system are treated successfully by simply interrupting the vein that drains the dural AVF as it enters the subarachnoid space. The authors identified a subgroup of patients with cranial dural AVF's in whom the AVF was drained only by leptomeningeal veins, and sought to establish whether simple interruption of the vein draining the blood from the AVF into the subarachnoid space is effective and lasting treatment in this subgroup of patients, as it is in patients with spinal dural AVF's.

Four adult patients with symptomatic cranial dural AVF's (two petrotentorial, one middle fossa floor, and one posterior fossa base) were identified on arteriography as having fistulae that were supplied by the internal and/or external carotid arteries and drained only via leptomeningeal veins (two entered the petrosal vein, one a cerebellar hemispheric vein, and one a mesencephalic vein). All patients underwent interruption of the vein draining the dural AVF as it penetrated the dura to enter the subarachnoid space, and experienced neurological improvement after surgery. Repeat arteriography at 1 to 2 weeks (three patients), 3 months (3 patients), 12 to 15 months (three patients), and 4 years (two patients) revealed no residual AVF and no evidence of abnormal blood flow.

Many cranial dural AVF's with leptomeningeal venous drainage (the type with the most aggressive behavior) are drained only by leptomeningeal veins. This subgroup of patients can be identified by selective arteriography and requires only interruption of the draining vein as it enters the subarachnoid space for successful, lasting elimination.