Primary Extra-axial Glioblastoma: Case Report and Literature Review

Glioblastoma multiforme (GBM) is the most frequent and most aggressive primary brain tumor in adults,mainly located in the cerebral hemispheres. In the literature, few cases of primary GBM have been reported to have radiographic and intraoperative features of extra-axial lesions, leading to a diagnostic dilemma. Despite the advances in imaging modalities, the diagnosis of GBM can be challenging, and it is mainly based on the histopathologic confirmation of the excised tumor. We describe the case of a 76- year-old previously healthy female patient who presented to our hospital due to speech disturbances and cognitive impairment. The diagnosis of the tumor type on magnetic resonance imaging (MRI) was difficult, as the findings were suggestive of a malignant meningioma due to the heterogeneous enhancement of a dural-based mass with a dural tail sign. Moreover, the intraoperative findings revealed an extra-axial mass attached to the dura. A histological examination confirmed the diagnosis of glioblastoma with arachnoid infiltration. The patient underwent adjuvant radiotherapy and concomitant temozolomide treatment, she had clinical improvement postoperatively, and was stable during the six months of follow-up. Glioblastoma should be considered in the differential diagnosis of primary extra-axial mass with atypical and malignant features, especially in elderly patients.

Comparison among ACR1997, SLICC and the new EULAR/ACR classification criteria in childhood-onset systemic lupus erythematosus

Abstract Background: To date there are no specific classification criteria for childhood-onset systemic lupus erythematosus (cSLE). This study aims to compare the performance among the American College of Rheumatology (ACR) 1997, the Systemic Lupus International Collaborating Clinics criteria (SLICC) and the new European League Against Rheumatism (EULAR)/ACR criteria, in a cSLE cohort. Methods: We conducted a medical chart review study of cSLE cases and controls with defined rheumatic diseases, both ANA positive, to establish each ACR1997, SLICC and EULAR/ACR criterion fulfilled, at first visit and 1-year-follow-up. Results: Study population included 122 cSLE cases and 89 controls. At first visit, SLICC criteria had higher sensitivity than ACR 1997 (89.3% versus 70.5%, p < 0.001), but similar specificity (80.9% versus 83.2%, p = 0.791), however performance was not statistically different at 1-year-follow-up. SLICC better scored in specificity compared to EULAR/ACR score ≥ 10 at first visit (80.9% versus 67.4%, p = 0.008) and at 1-year (76.4% versus 58.4%, p = 0.001), although sensitivities were similar. EULAR/ACR criteria score ≥ 10 exhibited higher sensitivity than ACR 1997 (87.7% versus 70.5%, p < 0.001) at first visit, but comparable at 1-year, whereas specificity was lower at first visit (67.4% versus 83.2%, p = 0.004) and 1-year (58.4% versus 76.4%, p = 0.002). A EULAR/ACR score ≥ 13 against a score ≥ 10, resulted in higher specificity, positive predictive value, and cut-off point accuracy. Compared to SLICC, a EULAR/ACR score ≥ 13 resulted in lower sensitivity at first visit (76.2% versus 89.3%, p < 0.001) and 1-year (91% versus 97.5%, p = 0.008), but similar specificities at both assessments. When compared to ACR 1997, a EULAR/ACR total score ≥ 13, resulted in no differences in sensitivity and specificity at both observation periods. Conclusions: In this cSLE population, SLICC criteria better scored at first visit and 1-year-follow-up. The adoption of a EULAR/ACR total score ≥ 13 in this study, against the initially proposed ≥10 score, was most appropriate to classify cSLE. Further studies are necessary to address if SLICC criteria might allow fulfillment of cSLE classification earlier in disease course and may be more inclusive of cSLE subjects for clinical studies.

Cauda Equina Syndrome Occurred by Adhesive Arachnoiditis of the Lumbar Spine with an Unknown Cause / 대한정형외과학회잡지

Spinal adhesive arachnoiditis is an inflammation and fibrosis of the subarachnoid space and pia mater caused by infection, trauma, spinal vascular anomalies, and iatrogenic (surgery and/or puncture). Adhesive arachnoiditis develops various symptoms and signs (gait disturbances, radiating pain, paralysis, and incontinence). On the other hand, adhesive arachnoiditis associated with cauda equina syndrome has not been reported in Korea until now. The authors experienced cauda equina syndrome caused by adhesive arachnoiditis of the lumbar spine with satisfactory results following decompression. We report this case with a review of the relevant literature.

Spontaneous Disappearance of an Arachnoid Cyst after Burr Hole Drainage of Chronic Subdural Hematoma / 대한신경손상학회지

It is well known that the presence of arachnoid cysts (ACs) in young patients is a risk factor for developing a chronic subdural hematoma (CSDH) after a minor head injury. Although there have been controversies with the treatment, most authors recommend only draining the CSDH if the AC is asymptomatic. This judgement is based on the facts that this surgical approach has shown good clinical outcomes, and the AC usually remains unchanged after the surgery. Our case demonstrates that the AC of a young patient who developed a CSDH after a minor head injury completely disappeared after a burr hole drainage of the CSDH. Although the chances of an AC disappearing are low, this case shows that an AC might disappear after only draining a CSDH when a rupture of the AC membrane is identified. In such cases, we recommend first draining only the CSDH for the treatment of AC-associated CSDHs.

Disappearance of Arachnoid Cyst after Burrhole Trephination: Case Series / 대한신경손상학회지

We report 3 cases of arachnoid cysts (ACs) that completely disappeared after burr hole drainage, without cyst fenestration into the subarachnoid space or cystoperitoneal shunt. The first patient was a 21-year-old female with an AC of the right cerebral convexity, found incidentally. After endoscopic AC fenestration was performed, the patient complained of persistent headache. Two-month postoperative brain imaging revealed reaccumulated AC and associated multi-stage subdural hematoma. Burr hole drainage was performed to resolve the chronic subdural hematoma (CSDH). Three months later, brain computed tomography showed that the CSDH and the AC had disappeared. The second patient was an 11-year-old male who had a history of trauma 1 month prior to presentation at the clinic. Brain magnetic resonance imaging revealed an AC in the left sylvian fissure with CSDH. We performed burr hole drainage to treat the CSDH first. Subsequently, the AC as well as the CSDH disappeared. The third case was an AC of the right parietal convexity, found incidentally. Only burr hole drainage was performed, following which, the AC disappeared. This case series shows that an AC can disappear naturally after rupture into the subdural space by trauma or the burr hole procedure.

Cervical Cerebrospinal Fluid Leakage Concomitant with a Thoracic Spinal Intradural Arachnoid Cyst / 대한신경손상학회지

We encountered a very rare case of spontaneous spinal cerebrospinal fluid (CSF) leakage and a spinal intradural arachnoid cyst (AC) that were diagnosed at different sites in the same patient. These two lesions were thought to have interfered with the disease onset and deterioration. A 30-year-old man presented with sudden neck pain and orthostatic headache. Diplopia, ophthalmic pain, and headache deteriorated. CSF leakage was confirmed in C2 by radioisotope cisternography, and an epidural blood patch was performed. While his symptoms improved gradually, paraparesis suddenly progressed. Thoracolumbar magnetic resonance imaging (MRI) revealed an upper thoracic spinal intradural AC, which was compressing the spinal cord. We removed the outer membrane of the AC and performed fenestration of the inner membrane after T3-4 laminectomy. Postoperative MRI showed complete removal of the AC and normalized lumbar subarachnoid space. All neurological deficits including motor weakness, sensory impairment, and voiding function improved to normal. We present a case of spontaneous spinal CSF leakage and consecutive intracranial hypotension in a patient with a spinal AC. Our report suggests that if spinal CSF leakage and a spinal AC are diagnosed in one patient, even if they are located at different sites, they may affect disease progression and aggravation.

Modified Arachnoid Plasty Reduces Chronic Subdural Hematoma after Unruptured Aneurysm Clipping : Technical Note

OBJECTIVE: Chronic subdural hematoma (CSDH) is a rare complication of unruptured intracranial aneurysm (UIA) clipping surgery. To prevent postoperative CSDH by reducing subdural fluid collection, we applied the modified arachnoid plasty (MAP) during the UIA clipping surgery to seal the dissected arachnoid plane.METHODS: This retrospective study included 286 patients enrolled from July 2012 to May 2015. We performed arachnoid plasty in all patients, with MAP used after June 17, 2014. Patients were divided into two groups (non-MAP vs. MAP), and by using uni- and multivariate analyses, baseline characteristics, and relationships with postoperative CSDH between the two groups were analyzed. The degree of preoperative brain atrophy was estimated using the bicaudate ratio (BCR) index.RESULTS: Ten patients (3.5%) among 286 patients had postoperative CSDH after clipping. Nine (3.1%) were in the non-MAP group, and one (0.9%) was in the MAP group. The higher BCR index showed statistical significance with occurrence of postoperative CSDH in both uni- (p=0.018) and multivariate (p=0.012; odds ratio [OR], 8.547; 95% confidence interval [CI], 1.616–45.455) analyses. MAP was associated with a lower risk of postoperative CSDH (p=0.022; OR, 0.068; 95% CI, 0.007–0.683).CONCLUSION: This study shows that the degree of preoperative brain atrophy is associated with an increased occurrence of CSDH after clipping and that MAP could help reduce the risk of postoperative CSDH after unruptured aneurysm clipping via a lateral supraorbital approach.

Modified Arachnoid Plasty Reduces Chronic Subdural Hematoma after Unruptured Aneurysm Clipping : Technical Note

OBJECTIVE: Chronic subdural hematoma (CSDH) is a rare complication of unruptured intracranial aneurysm (UIA) clipping surgery. To prevent postoperative CSDH by reducing subdural fluid collection, we applied the modified arachnoid plasty (MAP) during the UIA clipping surgery to seal the dissected arachnoid plane. METHODS: This retrospective study included 286 patients enrolled from July 2012 to May 2015. We performed arachnoid plasty in all patients, with MAP used after June 17, 2014. Patients were divided into two groups (non-MAP vs. MAP), and by using uni- and multivariate analyses, baseline characteristics, and relationships with postoperative CSDH between the two groups were analyzed. The degree of preoperative brain atrophy was estimated using the bicaudate ratio (BCR) index. RESULTS: Ten patients (3.5%) among 286 patients had postoperative CSDH after clipping. Nine (3.1%) were in the non-MAP group, and one (0.9%) was in the MAP group. The higher BCR index showed statistical significance with occurrence of postoperative CSDH in both uni- (p=0.018) and multivariate (p=0.012; odds ratio [OR], 8.547; 95% confidence interval [CI], 1.616–45.455) analyses. MAP was associated with a lower risk of postoperative CSDH (p=0.022; OR, 0.068; 95% CI, 0.007–0.683). CONCLUSION: This study shows that the degree of preoperative brain atrophy is associated with an increased occurrence of CSDH after clipping and that MAP could help reduce the risk of postoperative CSDH after unruptured aneurysm clipping via a lateral supraorbital approach.

Subarachnoid Hemorrhage with Subdural Hematoma due to Ruptured De Novo Aneurysm after Aneurysmal Clipping via Pterional Approach: An Autopsy Case / 대한법의학회지

Subdural hematoma (SDH) due to spontaneous rupture of intracranial aneurysm rarely occurs. The prevalence of subarachnoid hemorrhage (SAH) with SDH is approximately 0.5%–10.3% of all aneurysmal SAH. We report a case of aneurysmal rupture with SDH and SAH due to arachnoid defect after aneurysm clipping. The decedent was a 51-year-old woman who underwent brain surgery for SAH a few years ago. Two days before she died, she had nausea and sentinel headache. She was alive in the morning and was found dead at 6 PM. Injuries in the external surface were not found. A fresh SDH, measured approximately 90 mL, was found in the right hemisphere. SAH was diffusely distributed at the base of the brain and the right sylvian fissure. Two aneurysmal clippings were found in the anterior communicating artery and right internal carotid artery. A ruptured de novo aneurysm was also found in the right proximal middle cerebral artery. An uncal herniation was also observed. The cause of death was SAH with SDH due to de novo intracranial aneurysm. The tearing caused by the adhesion between the aneurysm and arachnoid, high blood pressure, and massive bleeding has been thought to be the causative mechanism of aneurysmal SAH with SDH. However, in this case, the arachnoid defect was caused by aneurysmal clipping through pterional approach. This defect served as the passage between the subarachnoid and subdural spaces. The autopsy for recurrent intracranial aneurysm will increase according to the extending life expectancy of patients after aneurysmal clipping.

Hypomania in Bobble-Head Doll Syndrome: A Case Report of Surgically Treated Stereotypy and Hypomania

A 22-year-old man was admitted with gradually aggravating stereotypic head movement with hypomania. Brain magnetic resonance imaging showed a large suprasellar arachnoid cyst extending into the third ventricle, with obstructive hydrocephalus, characteristic of bobble-head doll syndrome. Endoscopic fenestration of the suprasellar arachnoid cyst was performed. Stereotypic head movement stopped immediately after surgery and hypomanic symptoms gradually improved within a month. During 4 years of follow-up observation without medication, neuropsychiatric symptoms did not relapse. We report our experience of surgically treating stereotypy and hypomania in a case of bobble-head doll syndrome and discuss the possible neuropsychiatric mechanisms of this rare disease.

A Rare Cause of Thoracic Spinal Cord Compression by Multiple Large Tarlov Cysts / 대한신경손상학회지

Spinal extradural arachnoid cyst (SEAC) is a rare cause of spinal cord compression. Bifocal location of thoracic and sacral SEACs is rarely reported in the literature. We report a case of thoracic spinal cord compression by SEAC associated with asymptomatic multiple sacral Tarlov cysts (TC). The surgical management and postoperative outcome of the patient are discussed. A 34-year-old woman was referred to the hospital for acute thoracic pain with a history of chronic long-standing back pain. She complained of walking difficulties. Neurological examination demonstrated incomplete spastic paraplegia with sensory level in T9. Magnetic resonance imaging revealed a large cystic formation from T7-11 and at the level of the sacrum. We performed laminectomies at the level of interest from T7-11. The cysts were dissected from the underlying dura after removal of the cerebrospinal fluid. We found nerve tissue in the cysts. We excised the cyst and preserved the nerve roots. Subsequently, a duraplasty was performed with autologous grafts from the lumbar fascia. The condition of the patient improved after surgery and he was recovering well at follow-up. Although the surgical treatment of TC is controversial, especially at the sacral lumbar level, decompression at the dorsal level in this case is indisputable.

Primary extracranial meningioma presenting as a forehead mass

Meningioma originates from arachnoid cap cells and is the second most common intracranial tumor; however, it can also be found in an extracranial location. A very rare primary extracranial meningioma without the presence of an intracranial component has also been reported. Primary extracranial meningiomas have been found in the skin, scalp, middle ear, and nasal cavity. A computerized tomography or magnetic resonance imaging scan is necessary to determine the presence or absence of an intracranial meningioma, and a biopsy is essential for diagnosis. We report a case of primary extracranial meningioma located in the forehead skin of a 51-year-old male.

Arachnoid Granulations Mimicking Multiple Osteolytic Bone Lesions in the Occipital Bone

We report a rare case of arachnoid granulations mimicking multiple osteolytic bone lesions. A 66-year-old woman was admitted to a local clinic for a regular checkup. Upon admission, brain CT showed multiple osteolytic lesions in the occipital bone. These needed to be differentiated from multiple osteolytic bone tumor. Subsequent brain MRI revealed that the osteolytic lesions were isointense to cerebrospinal fluid, hyperintense on T2-weighted image, hypointense on T1-weighted image, and with subtle capsules around the osteolytic lesions that were visible after gadolinium injection. A bone scan revealed no radiotracer uptake. The lesions were in both the transverse sinuses and the torcular herophili. With typical radiological appearances of the lesions, the osteolytic lesions were diagnosed as multiple arachnoid granulations. No further treatment was planned. A 1-year follow-up brain CT scan revealed no change. We should consider the possibility of arachnoid granulations when multiple osteolytic lesions are observed in the occipital bone.

Caracterización del realce meníngeo intracraneal / Intracranial Meningeal Enhancement Characterization

Objetivo: Describir las características del realce meníngeo intracraneal (RMI) como hallazgo en resonancia magnética y su comportamiento según las diferentes patologías asociadas descritas en la literatura científica. Materiales y métodos: Estudio descriptivo de corte transversal realizado con información recolectada de 89 estudios, entre enero y diciembre de 2011, en los cuales se encontró realce meníngeo como hallazgo positivo en la lectura original. Cada estudio fue sometido a nueva revisión por un neurorradiólogo para la caracterización morfológica del realce meníngeo. Resultados: Las causas más frecuentes de RMI fueron enfermedad metastásica (21,3 %), etiología infecciosa (21,3 %), antecedente de cirugía intracraneal (20,2 %) y neoplasias primarias (13,5 %). Del total de las infecciones del sistema nervioso central (19 casos) se documentó infección por VIH en 12 pacientes (70,6 %). El paciente con antecedente quirúrgico de mayor antigüedad fue sometido a craneotomía 17 años antes de la toma de la resonancia magnética incluida en el estudio, en la cual persiste el realce aunque no se han definido signos de recidiva por imagen o por clínica hasta 2015. El tipo de realce más frecuente fue el leptomeníngeo (46,1 %), seguido del mixto (43,8 %) y el paquimeníngeo (10,1 %). En el subgrupo de realce leptomeníngeo, las etiologías más frecuentes fueron infecciosa (31,7 %), enfermedad metastásica (19,5 %) y neoplasias primarias (17,1 %), persistiendo esta tendencia en el subgrupo de realce paquimeníngeo. En el subgrupo de realce mixto, la etiología posquirúrgica fue la primera causa (35,9 %), seguida de la enfermedad metastásica (23,1 %) y las infecciones (18 %). En los casos de etiología infecciosa se encontró un predominio del patrón de realce leptomeníngeo, nodular y difuso, sin realce paquimeníngeo, como único tipo de realce. Conclusión: Aunque un patrón de realce meníngeo determinado no es indicativo de una patología específica, el estudio detallado de sus características puede aportar información que permite plantear grupos diagnósticos, particularmente en casos de etiología neoplásica o infecciosa, aporte de relevancia en casos en que el realce meníngeo anormal es la única alteración evidente en una resonancia magnética.

Objective: To describe the characteristics of intracranial meningeal enhancement (IME) as magnetic resonance imaging findings and their behavior under different associated conditions as described in the scientific literature. Materials and methods: Descriptive cross-sectional study with data collected from the images archive between January and December of 2011, obtaining 89 eligible studies in which it was determined, in the original reading, presence of IME as positive finding. Each study was subjected to further review by a neuroradiologist of the institution for morphological characterization of the IME. Results: The most common causes of IME were: metastatic disease (21.3%), infectious etiology (21.3%), history of intracranial surgery (20.2%) and primary neoplasms (13.5%). Of total CNS infections (19 cases), HIV infection was documented in 12 patients (70.6%). The patient with the oldest surgical history underwent craniotomy 17 years before performing the MRI included in the study, with persistance of IME with no signs of recurrence defined by image or clinical manifestations up to 2015. The most frequent IME type was leptomeningeal (LME) (46.1%), followed by mixed (MME) (43.8%) and pachymeningeal (PME) (10.1%) enhancements. In the subgroup of LME, the most common etiologies were: infectious (31.7%), metastatic disease (19.5%) and primary neoplasms (17.1%). This trend persisted in the subgroup of PME. In the subgroup of MME, post-surgical etiology was the leading cause (35.9%), followed by metastatic disease (23.1%) and infections etiologies (18%). Conclusion: Although a particular pattern of meningeal enhancement is not indicative of a specific pathology, detailed study of its features can provide information that allow the proposal of diagnostic groups, particularly in cases of neoplastic or infectious etiology, relevant contribution in cases where the abnormal meningeal enhancement is the only anormality in MRI.

Primary Central Nervous System Vasculitis Mimicking a Cortical Brain Tumor: A Case Report

We report a case of primary central nervous system vasculitis (PCNSV) mimicking a cortical brain tumor. A 25-year-old woman presented with a 2-week history of headache and transient right hemiparesis. Brain magnetic resonance imaging (MRI) revealed a cortical-involving lesion on the left frontal lobe. The 6-cm sized lesion showed low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. The lesion had continual linear enhancement on the subcortical white matter and leptomeninges. There was no evidence of hemorrhage on susceptibility-weighted images and no diffusion restriction on diffusion-weighted images. The regional cerebral blood volume was decreased on the MR perfusion images, and spectroscopy showed increased lactate and lipid peaks. The symptoms were aggravated by fever and seizures. Biopsy was performed to rule out tumorous or inflammatory lesions. Pathologically, lymphocytes were infiltrated on the vessels, and the arachnoid membrane was thickened with inflammatory cells. The patient did not have any underlying diseases, including immune disorders. After high-dose steroid administration, her symptoms improved. Two months later, brain MRI showed a reduction in the infiltration of the T2 hyperintensity lesion with subtle subcortical enhancement. We present a case of PCNSV involving the left frontal lobe, showing vasogenic edema, mass effect, and subcortical linear contrast enhancement without hemorrhage or infarction.

Collision Tumor Composed of Meningioma and Cavernoma

A true collision tumor is a rare entity composed of two histologically distinct neoplasms coinciding in the same organ. This paper reports a unique case of cerebral collision tumor consisting of two benign components. On the first hand, meningioma which is usually a benign lesion arising from the meningothelial cell in the arachnoidal membrane. On the other, cerebral cavernoma which is a well-circumscribed, benign vascular hamartoma within the brain. To our knowledge, there is no previously documented case of cerebral collision tumor consisting of two benign components. A 56-year-old Caucasian male suffered in 2002 from an atypical meningioma WHO II° located in the left lateral ventricle. Three years after the tumor extirpation, the patient suffered from a hematoma in the fourth ventricle due to a recurrently haemorrhaged cavernoma. In 2008, a recurrence of the tumor in the left lateral ventricle was discovered. Additionally, another tumor located in the quadrigeminal lamina was detected. After surgical resection of the tumor in the left lateral ventricle, the pathological examination confirmed the diagnosis of a collision tumor consisting of components of a meningioma WHO II° and a cavernoma. Postoperatively, no adjuvant treatment was needed and no tumor recurrence is discovered up to the present. A possible explanation for the collision of those two different tumors may be migration of tumor cells mediated by the cerebrospinal fluid. After 5-years of follow-up, there is no sign of any tumor recurrence; therefore, surgical tumor removal without adjuvant therapy seems to be the treatment of choice.

A Case of Endoscopic Transethmoidal Drainage of Subdural Abscess Originated from Dental Infection / 대한이비인후과학회지

Subdural empyema is fulminating purulent infection that develops between the dura and the arachnoid membranes. It is rare but one of the most immediate of neurosurgical emergencies, hence the importance of proper diagnosis and early intervention. Most subdural empyema complicated in the ENT field originate from sinonasal or otologic infections rather than dental infections. In our case of 64-years-old male, who was admitted with headache and fever, the diagnosed subdural empyema originated from odontogenic parapharyngeal abscess. We report that the case was successfully managed after urgent surgical drainage by endoscopic transethmoidal approach with long term intravenous antibiotics.

Considerations in Treating Neonatal and Infantile Patients with a Retrocerebellar Arachnoid Cyst: in the Perspective of Different CSF Dynamics / 대한소아신경학회지

Arachnoid cysts found under the age of 1 year are more likely to grow in size, relatively short term follow-up is required. Retrocerebellar location predicts a high risk of hydrocephalus, and the time window until irreversible neuronal damage is often narrow if the arachnoid cyst increases in size and becomes symptomatic. However, when and how to treat a neonatal or infantile patient with a retrocerebellar arachnoid cyst is still a controversial subject. We recently experienced 3 differently treated very young pediatric patients with retrocerebellar arachnoid cysts. One patient was treated two weeks after birth by a cystoperitoneal shunt. This patient showed normal development after the surgery. The other patient was treated by a ventriculoperitoneal shunt and subsequent cystoventriculostomy at the age of 4 months because of his mother's refusal on 14th day after birth. This one showed developmental delay despite of decreasing size of ventricles after the surgery. The last patient was treated with microscopic fenestration, which failed in its initial attempt. A revision operation by cyst excision succeeded and had no problem after the surgery. Therefore, we suggest that early surgical intervention for retrocerebellar arachnoid cyst can be considered. Although there are concerns of long term complications related to shunts, a cystoperitoneal shunt would be a feasible treatment if we consider the minor cerebrospinal fluid pathway which is the dominant cerebrospinal fluid dynamic at this age.

Postoperative Spinal Subdural Lesions Following Lumbar Spine Surgery: Prevalence and Risk Factors

STUDY DESIGN: Retrospective case–control study PURPOSE: To clarify the prevalence and risk factors for spinal subdural lesions (SSDLs) following lumbar spine surgery. OVERVIEW OF LITERATURE: Because SSDLs, including arachnoid cyst and subdural hematoma, that develop following spinal surgery are seldom symptomatic and require reoperation, there are few reports on these pathologies. No study has addressed the prevalence and risk factors for SSDLs following lumbar spine surgery. METHODS: We conducted a retrospective analysis of the magnetic resonance (MR) images and medical records of 410 patients who underwent lumbar decompression surgery with or without instrumented fusion for degenerative disorders. SSDLs were classified into three grades: grade 0, no obvious lesion; grade 1, cystic lesion; and grade 2, lesions other than a cyst. Grading was based on the examination of preoperative and postoperative MR images. The prevalence of SSDLs per grade was calculated and risk factors were evaluated using multivariate logistic regression analysis. RESULTS: Postoperative SSDLs were identified in 123 patients (30.0%), with 50 (12.2%) and 73 (17.8%) patients being classified with grade 1 and 2 SSDLs, respectively. Among these, one patient was symptomatic, requiring hematoma evacuation because of the development of incomplete paraplegia. Bilateral partial laminectomy was a significantly independent risk factor for SSDLs (odds ratio, 1.52; 95% confidence interval, 1.20–1.92; p<0.001). In contrast, a unilateral partial laminectomy was a protective factor (odds ratio, 0.11; 95% confidence interval, 0.03–0.46; p=0.002). CONCLUSIONS: The prevalence rate of grade 1 SSDLs was 30%, with no associated clinical symptoms observed in all but one patient. Bilateral partial laminectomy increases the risk for SSDLs, whereas unilateral partial laminectomy is a protective factor.