Takafumi Shimogawa

Arterial Spin Labeling Perfusion Magnetic Resonance Image with Dual Postlabeling Delay: A Correlative Study with Acetazolamide Loading 123I-Iodoamphetamine Single-Photon Emission Computed Tomography

BACKGROUND Perfusion magnetic resonance image with arterial spin labeling (ASL) provides a completely noninvasive measurement of cerebral blood flow (CBF). However, arterial transient times can have a marked effect on the ASL signal. For example, a single postlabeling delay (PLD) of 1.5 seconds underestimates the slowly streaming collateral pathways that maintain the cerebrovascular reserve (CVR). To overcome this limitation, we developed a dual PLD method. SUBJECTS AND METHODS A dual PLD method of 1.5  and 2.5 seconds was compared with (123)I-iodoamphetamine single-photon emission computed tomography with acetazolamide loading to assess CVR in 10 patients with steno-occlusive cerebrovascular disease. RESULTS In 5 cases (Group A), dual PLD-ASL demonstrated low CBF with 1.5-second PLD in the target area, whereas CBF was improved with 2.5-second PLD. In the other 5 cases (Group B), dual PLD-ASL depicted low CBF with 1.5-second PLD, and no improvement in CBF with 2.5-second PLD in the target area was observed. On single-photon emission computed tomography, CVR was maintained in Group A but decreased in Group B. CONCLUSIONS Although dual PLD methods may not be a completely alternative test for (123)I-iodoamphetamine single-photon emission computed tomography with acetazolamide loading, it is a feasible, simple, noninvasive, and repeatable technique for assessing CVR, even when employed in a routine clinical setting.

Arterial Spin-Labeling Magnetic Resonance Perfusion Imaging with Dual Postlabeling Delay in Internal Carotid Artery Steno-occlusion: Validation with Digital Subtraction Angiography

BACKGROUND Arterial spin-labeling magnetic resonance perfusion imaging (ASL-MRI) allows noninvasive measurement of cerebral blood flow (CBF) but depends on the arterial transit time (ATT). With the commonly used single postlabeling delay (PLD) of 1.5 seconds, slow flow through collateral vessels may be underestimated. We used both 1.5 and 2.5 seconds to overcome this problem. We validated these PLD settings by measuring the ATT and identifying the angiographic circulation using digital subtraction angiography (DSA). METHODS We retrospectively selected 5 patients with unilateral occlusion or stenosis of the internal carotid artery (ICA) in whom ASL-MRI showed low CBF with 1.5-second PLD in the target area and improved CBF with 2.5-second PLD. We then compared the ASL-MRI findings visually with DSA findings at 1.5 and 2.5 seconds after injection of the contrast. When arterial transit artifacts (ATAs), attributed to stagnant intravascular spin-labeled blood, were observed, DSA findings were analyzed visually at 4.5 seconds. RESULTS DSA revealed that the hypovascular area seen at 1.5 seconds was improved via the primary and secondary collaterals and delayed anterograde flow at 2.5 seconds. Serpiginous or round-shaped ATAs, which appeared in nearly the same configuration on dual PLD ASL-MRI, were attributed to stagnant collaterals and flow in the M2 portion of the middle cerebral artery and ICA during the late venous phase. CONCLUSIONS Use of dual PLD times was validated by the DSA findings. ATA detection using the dual PLDs also differentiated well-developed and stagnant collateral vessels from focal hyperperfusion.

Concurrent spinal nerve root schwannoma and meningioma mimicking single-component schwannoma.

We present a first case of concurrent tumors consisting of schwannoma and meningioma arising at the same spinal level in a patient without neurofibromatosis. A 49‐year‐old man without clinical evidence of neurofibromatosis presented with a 5‐month history of right neck pain. MRI demonstrated an extradural tumor involving the right‐sided C2 nerve root with a small intradural component. T1‐ and T2‐weighted and contrast‐enhanced MRI could not differentiate the intradural tumor as different from the extradural tumor. Total removal of the tumors was performed. No contiguity of the extradural tumor with the intradural tumor was seen. The intradural tumor attached strongly to the dura mater around the C2 nerve root exits. Intraoperative pathological diagnosis confirmed the extradural tumor as schwannoma and the intradural tumor as meningioma. We therefore thoroughly coagulated the dura mater adjacent to the intradural tumor and resected the dura mater around the nerve root exits together with the tumor. Pathological examination revealed that the resection edge of the extradural component consisted of a spinal nerve with thickened epineurium and was free of neoplastic cells. No schwannoma component was evident in the intradural tumor. No obvious transition thus existed between the extra‐ and intradural tumors. Distinguishing these tumors prior to surgery is critical for determining an optimal surgical plan, as schwannoma and meningioma require different surgical procedures. We therefore recommend a careful review of preoperative imaging with the possibility of concurrent tumors in mind.

Neurosurgical management and pathology of lumbosacral lipomas with tethered cord

Lumbosacral lipomas are the most common form of occult spinal dysraphism. The development of lumbosacral lipomas is from the premature disjunction of the neural tube from the surrounding ectoderm, leaving the neural plate open posteriorly and allowing for the infiltration of mesodermal tissue, including fatty tissue. Since lumbosacral lipomas are a common cause of spinal cord tethering that can lead to progressive neurological deficits, prophylactic neurosurgery for lumbosacral lipomas, including untethering of the spinal cord, is recommended. We briefly review the embryology, classification, clinical presentation, imaging evaluation, surgical indication, neurosurgical management and pathological examination that are involved in recognizing these complicated malformative pathologies.

Neurosurgical pathology of limited dorsal myeloschisis

PurposeThe term limited dorsal myeloschisis (LDM) was used by Pang et al. (2010) to describe a distinct clinicopathological entity. LDMs are characterized by two invariable features: a focal-closed neural tube defect and a fibroneural stalk that links the skin lesion to the underlying spinal cord.MethodsWe retrospectively analyzed the neurosurgical pathologic findings of four LDM patients.ResultsCase 1 had a saccular skin lesion with nonterminal abortive myelocystocele at T11–12. Cases 2, 3, and 4 had a non-saccular (flat) skin lesion in the lumbosacral region. The morphologic features of the lesion in case 2 were those of meningocele manque. Cases 3 and 4 had accompanying non-LDM anomalies, caudal-type lipoma and type II split-cord malformation with neurenteric cyst, respectively. At preoperative diagnosis of the LDM stalk, magnetic resonance imaging, including 3D heavily T2-weighted image was useful; however, minute findings were often missed in the complicated cases 3 and 4. All patients had a favorable outcome following untethering of the stalk from the cord. The central histopathological feature of the LDM stalk is neuroglial tissue in the fibrocollagenous band; however, the stalk in cases 2 and 4 did not have glial fibrillary acidic protein-immunopositive neuroglial tissues.ConclusionsTherefore, the diagnosis of LDM should be made based on comprehensive evaluation of histologic and clinical findings.

Signal changes on magnetic resonance perfusion images with arterial spin labeling after carotid endarterectomy.

Background: Cerebral hyperperfusion after carotid endarterectomy (CEA) is defined as an increase in ipsilateral cerebral blood flow (CBF). Practically, however, prompt and precise assessment of cerebral hyperperfusion is difficult because of limitations in the methodology of CBF measurement during the perioperative period. Arterial spin labeling (ASL) is a completely noninvasive and repeatable magnetic resonance perfusion imaging technique that uses magnetically-labelled blood water as an endogenous tracer. To clarify the usefulness of ASL in the management of cerebral hyperperfusion, we investigated signal changes by ASL with a single 1.5-s post-labeling delay on visual inspection. Methods: Thirty-two consecutive patients who underwent CEA were enrolled in this retrospective study. Results: On postoperative day 1, 22 (68.8%) and 4 (12.5%) patients exhibited increased ASL signals bilaterally (Group A) and on the operated side (Group B), respectively. Follow-up ASL showed improvement in these findings. Six (18.8%) patients showed no change (Group C). There was no apparent correlation between ASL signals on postoperative day 1 and the preoperative hemodynamic state, including the cerebrovascular reserve (P = 0.2062). Three (9.4%) patients developed cerebral hyperperfusion syndrome (two in Group A and one in Group B). Coincidence in the localization of increased ASL signals and electroencephalographic abnormalities was noted in these patients. Conclusion: Visual analysis of ASL with a single post-labeling delay overestimates CBF and cannot identify patients at risk of cerebral hyperperfusion syndrome probably because of the strong effect of the shortened arterial transit time immediately after CEA. However, ASL may be used as for screening.

Retained medullary cord extending to a sacral subcutaneous meningocele

BackgroundA retained medullary cord (RMC) is a rare closed spinal dysraphism with a robust elongated neural structure continuous from the conus and extending to the dural cul-de-sac. One case extending down to the base of a subcutaneous meningocele at the sacral level has been reported.Clinical presentationWe report on three cases of closed spinal dysraphism, in which a spinal cord-like tethering structure extended out from the dural cul-de-sac and terminated at a skin-covered meningocele sac in the sacrococcygeal region, which was well delineated in curvilinear coronal reconstructed images of 3D-heavily T2-weighted images (3D-hT2WI). Intraoperative neurophysiology revealed the spinal cord-like tethering structure was nonfunctional, and histopathology showed that it consisted of central nervous system tissue, consistent with RMC. The tethering structure histologically contained a glioneuronal core with an ependymal-like lumen and smooth muscle, which may indicate developmental failure during secondary neurulation.ConclusionsWhen the RMC extending to a meningocele is demonstrated with the detailed magnet resonance imaging including 3D-hT2WI, decision to cut the cord-like structure for untethering of the nervous tissue should be made under careful intraoperative neurophysiological monitoring.

Optimal perioperative management of antithrombotic agents in patients with chronic subdural hematoma

OBJECTIVE The use of antithrombotic agents such as anticoagulants and antiplatelet agents is widespread, and the opportunities to treat patients with chronic subdural hematoma (CSDH) under antithrombotic therapy are growing. However, whether antithrombotic therapy contributes to postoperative complications and recurrences of CSDH and how these agents should be managed in the surgical treatment of CSDH remains unclear. METHODS We retrospectively analyzed 150 consecutive patients with CSDH who underwent neurosurgical interventions at Kyushu Rosai Hospital from 2011 to 2015 and followed them for more than 3 months. RESULTS Of the 150 study patients, 44 received antithrombotic therapy. All anticoagulants and 76% of the antiplatelet agents were discontinued before surgical treatment of CSDH and resumed within 1 week except in 4 patients whose treatment was terminated and 7 patients who developed postoperative complications or underwent reoperations before resumption of these agents. Postoperative hemorrhagic complications associated with surgical treatment of CSDH occurred in 8 patients (5.3%), and there was no significant difference in the incidence of these complications between patients with and without antithrombotic therapy (6.8% vs. 4.7%, respectively; p=0.90). Postoperative thromboembolic complications occurred in 5 patients (5.4%), including 4 patients with antithrombotic therapy; these complications developed before resumption of antithrombotic agents in 2 patients. There was a significant difference in the incidence of postoperative thromboembolic complications between patients with and without antithrombotic therapy (9.1% vs. 0.9%, respectively; p=0.04). There were no significant differences in the incidence of radiographic deterioration or reoperation of ipsilateral or contralateral hematomas between patients with and without antithrombotic therapy after surgical treatment of unilateral CSDH. CONCLUSION A history of antithrombotic therapy was significantly correlated with the incidence of postoperative thromboembolic complications in patients with CSDH. Antithrombotic agents should be resumed as soon as possible when no hemorrhagic complication is confirmed after neurosurgical intervention for CSDH.

Surgical histopathology of limited dorsal myeloschisis with flat skin lesion

PurposeLimited dorsal myeloschisis (LDM) is characterized by two invariable features: a focal closed neural tube defect and a fibroneural stalk linking the skin lesion to the underlying spinal cord. Although detailed histopathological findings of the LDM stalk were originally described by Pang et al., the precise relationship between the histopathological findings and clinical manifestations including intraoperative findings has not been fully determined.MethodsWe retrospectively analyzed the histopathological findings of the almost entire stalk and their relevance to the clinical manifestations in six Japanese LDM patients with flat skin lesions.ResultsGlial fibrillary acidic protein (GFAP)-immunopositive neuroglial tissues were observed in three of the six patients. Unlike neuroglial tissues, peripheral nerve fibers were observed in every stalk. In four patients, dermal melanocytosis, “Mongolian spot,” was seen surrounding the cigarette-burn lesion. In three of these four patients, numerous melanocytes were distributed linearly along the long axis of the LDM stalk, which might represent migration of melanocytes from trunk neural crest cells during formation of the LDM stalk.ConclusionImmunopositivity for GFAP in the LDM stalk was observed in as few as 50% of our patients, despite the relatively extensive histopathological examination. We confirm that the clinical diagnosis of LDM should be made based on comprehensive histopathological examination as well as clinical manifestations. The profuse network of peripheral nerve fibers in every stalk and the high incidence of melanocyte accumulation associated with dermal melanocytosis might assist the histopathological diagnosis of LDM.

Sequential changes of arterial spin-labeling perfusion MR images with dual postlabeling delay following reconstructive surgery for giant internal carotid artery aneurysm

Background: Arterial spin-labeling magnetic resonance perfusion imaging (ASL-MRI) allows noninvasive measurement of cerebral blood flow (CBF) but depends on arterial transit time (ATT). To overcome this problem, we developed a simple ASL technique with dual postlabeling delay (PLD) settings. In addition to the routinely used PLD of 1.5 seconds, we selected another PLD of 2.5 seconds to assess slowly streaming blood flow and detect arterial transit artifacts (ATAs) resulting from stagnant intravascular magnetically labeled spins. Case Description: We validated the dual PLD method with digital subtraction angiography (DSA) findings in a patient with an unruptured right giant internal carotid artery (ICA) aneurysm who underwent proximal ligation of the right cervical ICA followed by right superficial temporal artery–middle cerebral artery anastomosis. The giant aneurysm was detected as a strongly hyperintense signal area of ATA using both values of PLD. Decreased signal in the right hemisphere at PLD 1.5 seconds was somewhat improved at PLD 2.5 seconds. DSA revealed that this laterality resulted from the different ATT values between hemispheres due to stagnation of the labeled spin within the aneurysm. Postoperatively, with gradual but complete thrombosis and regression of the aneurysm, the size of the ASL hyperintense signal area decreased markedly. At postoperative 2 years, the aneurysm was not demonstrated as an ATA; furthermore, the decreased signals in the right hemisphere at PLD 1.5 seconds had mostly improved. Conclusion: Serial ASL-MRI with dual PLDs could show dynamic changes of giant aneurysms and the associated hemodynamic state following the surgery.