Angiographic evaluation of the distance from the top of the jugular bulb to the inferior petrosal sinus-internal jugular vein junction: simple classification and identification method for the orifice of the non-visualized inferior petrosal sinus during neuroendovascular surgery.

BACKGROUND: The inferior petrosal sinus (IPS) is the transvenous access route for neurointerventional surgery that is occasionally undetectable on digital subtraction angiography (DSA) because of blockage by a clot or collapse. This study was aimed at analyzing the distance from the jugular bulb (JB) to the IPS-internal jugular vein (IJV) junction and proposing a new anatomical classification system for the IPS-IJV junction to identify the non-visualized IPS orifice. METHODS: DSA of 708 IPSs of 375 consecutive patients were retrospectively investigated to calculate the distance from the top of the JB to the IPS-IJV junction, and a simple classification system based on this distance was proposed. RESULTS: The median distance from the top of the JB to the IPS-IJV junction was 20.8 ± 14.7 mm. Based on the lower (10.9 mm) and upper (31.1 mm) quartiles, IPS-IJV junction variants were: type I, 0-10 mm (22.3%); type II, 11-30 mm (45.8%); type III, > 31 mm (23.9%); and type IV, no connection to the IJV (8.0%). Bilateral distances showed a positive interrelationship, with a correlation coefficient of 0.86. The bilateral symmetry type (visualized IPSs bilaterally) according to our classification occurred in 267 of 300 (89.0%) patients. CONCLUSIONS: In this study, the IPS-IJV junction was located far from the JB (types II and III), with a higher probability (69.6%). This distance and the four-type classification demonstrated high degrees of homology with the contralateral side. These results would be useful for identifying the non-visualized IPS orifice.

Adult Drosophila sensory neurons specify dendritic territories independently of dendritic contacts through the Wnt5-Drl signaling pathway.

Sensory neurons with common functions are often nonrandomly arranged and form dendritic territories in stereotypic spatial patterns throughout the nervous system, yet molecular mechanisms of how neurons specify dendritic territories remain largely unknown. In Drosophila larvae, dendrites of class IV sensory (C4da) neurons completely but nonredundantly cover the whole epidermis, and the boundaries of these tiled dendritic fields are specified through repulsive interactions between homotypic dendrites. Here we report that, unlike the larval C4da neurons, adult C4da neurons rely on both dendritic repulsive interactions and external positional cues to delimit the boundaries of their dendritic fields. We identify Wnt5 derived from sternites, the ventral-most part of the adult abdominal epidermis, as the critical determinant for the ventral boundaries. Further genetic data indicate that Wnt5 promotes dendrite termination on the periphery of sternites through the Ryk receptor family kinase Derailed (Drl) and the Rho GTPase guanine nucleotide exchange factor Trio in C4da neurons. Our findings thus uncover the dendritic contact-independent mechanism that is required for dendritic boundary specification and suggest that combinatory actions of the dendritic contact-dependent and -independent mechanisms may ensure appropriate dendritic territories of a given neuron.

[Cerebral Amyloid Angiopathy-related Inflammation Demonstrating Early Venous Filling on Digital Subtraction Angiography:A Case Report].

Cerebral amyloid angiopathy-related inflammation(CAA-RI)is a rare condition thought to be caused by an inflammatory response to amyloid beta(Aß)protein in the walls of the small arteries and capillaries of the cerebral cortex. A 73-year-old female presented with left hemiparesis and dysarthria. Fluid-attenuated inversion recovery(FLAIR)imaging disclosed progressive enlargement of infiltrative white matter abnormalities in the right temporo-occipito-parietal lobes. Interestingly, digital subtraction angiography(DSA)demonstrated early venous filling. Pathological examination of the biopsy specimen demonstrated lymphocytes infiltration surrounding the blood vessels and in the thickened walls with amyloid-beta deposition. The diagnosis given was CAA-RI. The patient was successfully treated with high dose corticosteroids and clinical improvement was associated with shrinkage of the high intensity lesion on FLAIR imaging. Early venous filling resolved on the follow-up DSA. Most patients with CAA-RI can be treated with corticosteroids. However, the clinical condition will worsen without appropriate treatment. Early diagnosis is the key. If an expanding disease of the white matter appears in an elderly patient, we should exclude other cerebrovascular diseases by DSA, followed by biopsy without delay. The present case demonstrated that early venous filling on DSA may appear until inflammation is resolved by the treatment of CAA-RI.

Angiographic Characterization of the External Carotid Artery: Special Attention to Variations in Branching Patterns.

Knowledge of branching patterns of external carotid artery (ECA) is essential for planning and execution of head and neck surgeries. Digital subtraction angiography (DSA) images of 532 ECAs from 302 consecutive patients were retrospectively evaluated. We classify the branch variants of ECA into three types, simply based on the number of branches arising close together. Type A, Type B, and Type C variants are defined as two, three, and four or more branches of ECAs arising at a common point from the proximal ECA, respectively. In this classification, the distal ECA was counted as one branch. Of 532 ECAs, Type A was found in 344 ECAs (64.6%) of 237 patients (78.5%), Type B in 134 ECAs (25.2%) of 110 patients (36.4%), and Type C in 54 ECAs (10.2%) of 49 patients (16.2%). The distance from the common carotid artery (CCA) bifurcation to the first branch of ECA with Type C was 14.7 ± 6.6 mm; its distance is shorter compared with Type A (21.8 ± 15.6 mm) and Type B (20.6 ± 8.9 mm) (P < 0.05). The position of CCA bifurcation with Type C was detected at the third-fourth junction cervical vertebral level or higher in 52 of 54 ECAs (96.3%), significantly higher than those of the other types (P < 0.05). In conclusion, Type C ECA has aggregated vessels with short distance from CCA and high position of CCA bifurcation. Type C ECA is not uncommon; thus, special consideration should be paid to avoid complications during surgeries.

Relationship between Stroke Events during Pachinko Play and Prognosis.

BACKGROUND: This study investigated whether pachinko play influences the outcome of stroke events, and identified the significant variables affecting outcomes. METHODS: We reviewed the medical and imaging records of 2075 consecutive patients with stroke from January 2003 through June 2012. The remaining patients were divided into 2 groups, the pachinko players group (PP) and the non-pachinko players group (NPP). Background factors were recorded on admission. Multivariate logistic regression analysis was used to identify the factors significantly correlated with Glasgow Outcome Scale (GOS) score and risk of death at the time of discharge. RESULTS: The PP group exhibited higher prevalence of hypertension and current smoking compared with the NPP group. However, no difference was found in outcomes between the PP and NPP groups. Multivariate analysis identified the dependent predictive variables for GOS as age (adjusted ß = -.18, 95% confidence interval [CI]: -.22 to -.14, P <.001), Glasgow Coma Scale (GCS) score on admission (adjusted ß = .64, 95% CI: .60 to .68, P <.001), and history of hypertension (adjusted ß = -.06, 95% CI: -.10 to -.02, P = .007). Logistic regression analysis showed that age (odds ratio = 1.02, 95% CI: 1.01 to 1.04, P <.001) and GCS score on admission (odds ratio = .72, 95% CI: .69 to .75, P <.001) were significantly associated with death at the time of discharge. CONCLUSIONS: Patients with stroke during playing pachinko have higher prevalence of hypertension and higher smoking rate, but pachinko play itself was not a critical factor determining the outcome of patients with stroke in our emergency center.

[Extendable Cords to Prevent Tumbling of a Suction Device during Craniotomy].

OBJECTIVE: Suction is necessary during craniotomy, and intraoperative tumbling of the suction device interrupts operative procedures. To avoid this, we developed a technique that would fasten the device to an extendable cord as is used to secure cell phones. SURGICAL TECHNIQUE: We used this technique in more than 300 craniotomies at the specific point of time when the suction device tends to tumble, i. e., during the opening and closure of a wound, which requires frequent instrument exchanges. Extendable cords fastened to the tip of the suction hose using a gift tie were attached to the drapes to secure the suction device next to the operative field. During the operation, the extendable cord followed the suction device manipulations. Consequently, although there was some tension in the cord during its extension, the maneuverability of the suction device was maintained. As the hanging suction device was closer to the operative field than devices stored in conventional pockets, its manipulation was easier and quicker. Upon release, the suction device automatically returned to its original position without distracting the surgeon. Tumbling of the device was prevented, and there were no procedure-related complications. CONCLUSIONS: Our simple modification using extendable cords prevented tumbling, avoided unnecessary replacements, and eased the manipulation of a suction device.

Excessive Heat Generation by Power-Driven Craniotomy Tools: A Possible Cause of Autologous Bone Flap Resorption Observed in an Ex Vivo Simulation.

BACKGROUND: Bone flap resorption is an issue after autologous cranioplasty. Critical temperatures above 50°C generated by power-driven craniotomy tools may lead to thermal osteonecrosis, a possible factor in resorption. This ex vivo study examined whether the tools produced excessive heat resulting in bone flap resorption. METHODS: Using swine scapulae maintained at body temperature, burr holes, straight and curved cuts, and wire-pass holes were made with power-driven craniotomy tools. Drilling was at the conventional feed rate (FR) plus irrigation (FR-I+), at a high FR plus irrigation (hFR-I+), and at high FR without irrigation (hFR-I-). The temperature in each trial was recorded by an infrared thermographic camera. RESULTS: With FR-I+, the maximum temperature at the burr holes, the cuts, and the wire-pass holes was 69.0°C, 56.7°C, and 46.2°C, respectively. With hFR-I+, these temperatures were 53.1°C, 52.1°C, and 46.0°C, with hFR-I- they were 56.0°C, 66.5°C, and 50.0°C; hFR-I- burr hole- and cutting procedures resulted in the highest incidence of bone temperatures above 50°C followed by FR-I+, and hFR-I+. At the site of wire-pass holes, only hFR-I- drilling produced this temperature. CONCLUSIONS: Except during prolonged procedures in thick bones, most drilling with irrigation did not reach the critical temperature. Drilling without irrigation risked generating the critical temperature. Knowing those characteristics may be a help to perform craniotomy with less thermal bone damage.

Complete removal of a cavernous malformation in the dorsal pons, in contact with the expanded transpontine vein: illustrative case.

BACKGROUND: Craniotomy is required for the removal of brainstem cavernous malformations (CMs) with repeated hemorrhage, and this condition is often complicated by an accompanying developmental venous anomaly (DVA). However, a DVA of the brainstem or cerebellum with drainage penetrating the pons is an exceptional finding. OBSERVATIONS: A 57-year-old man presented with double vision. Computed tomography revealed progressive enlargement of the hemorrhage in the dorsal pons. Contrast-enhanced magnetic resonance angiography revealed an expanded transverse vessel penetrating the center of the pons in contact with the CM. Digital subtraction angiography revealed that the DVA, comprising the expanded transpontine vein and some cerebellar medullary veins acting as normal venous drainage, coexisted with the CM. By utilizing the angioarchitecture and intraoperative neuronavigation system data, electrophysiological mapping, and indocyanine green videoangiography, complete removal of the CM was accomplished while preserving the DVA and brain function. LESSONS: This study presents the intraoperative images of an expanded transpontine vein as a DVA, which has never been depicted in a live patient before, accompanied by a CM in the dorsal portion of the pons. https://thejns.org/doi/10.3171/CASE24314.

Combination of neuroendoscopic hematoma evacuation and endovascular coil embolization for a ruptured anterior choroidal artery aneurysm in patients with moyamoya disease: illustrative cases.

BACKGROUND: The treatment strategy for hemorrhagic moyamoya disease (MMD) due to a ruptured aneurysm at the distal portion of the anterior choroidal artery remains controversial. The authors successfully treated the ruptured aneurysm with neuroendoscopic hematoma evacuation, followed by endovascular coil embolization. OBSERVATIONS: The authors encountered two patients with massive hemorrhagic MMD whose MMD had already been diagnosed and who had a periventricular anastomosis due to a ruptured aneurysm of the distal portion of the anterior choroidal artery involving the periventricular anastomosis. In both cases, neuroendoscopic hematoma evacuation was performed for hemorrhagic MMD in the acute phase, followed by endovascular coil embolization of the ruptured aneurysm in the chronic phase. In both endovascular treatments, the patient's condition was stabilized by hematoma evacuation, allowing a detailed preoperative evaluation of the anatomical findings of the vessel and functional findings of intraoperative neurophysiological monitoring using continuous monitoring of motor evoked potentials to preserve motor function. LESSONS: Combination therapy can be useful for hemorrhagic MMD in patients with diagnosed MMD with a periventricular anastomosis. Additionally, a preoperative understanding of the vascular construction and intraoperative neurophysiological monitoring will aid in the successful coil embolization of aneurysms at the distal portion of the anterior choroidal artery with hemorrhagic MMD.

The outcomes after anterior cruciate ligament reconstruction in adolescents with open physes.

PURPOSE: We evaluated the clinical outcome of anterior cruciate ligament reconstruction (ACLR) in adolescents with open physes and compared those results with adults. MATERIALS AND METHODS: Fifteen adolescents with open physes underwent physeal-sparing double-bundle ACLR using hamstring autograft. The median age of the adolescents was 14 years (range 13-16 years). Forty adults underwent anatomic double-bundle ACLR during the same period of this study. The median age of the adults was 26 years (range 17-39 years). Clinical outcomes were evaluated in terms of manual Lachman test, pivot shift test and the results of KT-2000 arthrometer. Additionally, we evaluated clinical outcome in terms of International Knee Documentation Committee (IKDC) score and Lysholm Knee Scoring Scale. We also evaluated rates of re-rupture. RESULTS: No clinically significant growth abnormalities were observed in adolescent cases. In the Lachman test, two of the 15 adolescents had a positive, whereas one of the 40 adults had a positive (n.s.). In the pivot shift test, three of the 15 adolescents had a positive, whereas two of the 40 adults had a positive (n.s.). There was no statistically significant difference between adolescents and adults, in the mean side-to-side difference in KT-2000 measurements (1.5 ± 1.5 mm vs. 1.1 ± 1.9 mm: n.s.), the median IKDC score (96.7 vs. 97.3: n.s.) and Lysholm Scale (99 vs. 98: n.s.), rates of re-rupture (13.3 vs. 7.5 %: n.s.). CONCLUSION: Physeal-sparing ACLR with hamstring autograft in adolescents with open physes resulted in good clinical outcomes similar to those of ACLR in adults without growth abnormalities.

Scratching and Stretching the Shrunken Cranial Dura for Primary Closure.

BACKGROUND: At craniotomy, the dura shrinks due to the drying effect of illumination and air exposure, rendering its primary closure difficult. When the opening is narrow, it can be patched with autologous grafts. However, tissue harvesting and meticulous suturing take time. As the cost-effectiveness of using dural substitutes is poor, we developed a new technique that involves dural scratching for the primary closure of dural openings. METHODS: We applied our technique because in 53 adults who underwent supratentorial craniotomy we encountered difficulties with the primary closure of a dural opening 5 mm or less in width. With a scalpel, we placed several fine scratches parallel to the edge of the opening on the surface of the dura, taking care not to perforate the deep layer. This relieved dural tension and the tissue was stretched enough to permit closing with sutures. RESULTS: Our technique achieved primary dural closure in 46 of 53 patients (87%) who primarily had undergone narrow supratentorial craniotomies. The other 7 additionally required small autologous grafts to patch narrow residual openings at the intersection of the durotomy. There were no procedure-related complications such as cerebrospinal fluid leakage and persistent headache due to tension of the closed dura. CONCLUSIONS: Dural scratching is simple, safe, requires no special instrumentation, facilitates primary closure of the shrunken dura by stretching, and reduces the need for patch grafting.

Frontotemporal Craniotomy for Clipping of Unruptured Aneurysm Using a Diamond-Coated Thread Wire Saw and Reconstruction Using Calcium Phosphate Cement without Metal Fixation.

Metal fixation systems for cranial bone flaps cut by a drill are convenient devices for cranioplasty, but cause several complications. We use modified craniotomy using a fine diamond-coated threadwire saw (diamond T-saw) to reduce the bone defect, and osteoplasty calcium phosphate cement without metal fixation. We report our outcomes and tips of this method. A total of 78 consecutive patients underwent elective frontotemporal craniotomy for clipping of unruptured intracranial aneurysms between 2015 and 2019. The follow-up periods ranged from 13 to 66 months. The bone fixation state was evaluated by bone computed tomography (CT) and three-dimensional CT (3D-CT). The diamond T-saw could minimize the bone defect. Only one wound infection occurred within 1 week postoperatively, and no late infection. No pain, palpable/cosmetically noticeable displacement of the bone flap, fluid accumulations, or other complications were observed. The condition of bone fixation and the cosmetic efficacy were thoroughly satisfactory for all patients, and bone CT and 3D-CT demonstrated that good bone fusion. No complication typical of metal fixation occurred. Our method is technically easy and safety, and achieved good mid-term bone flap fixation in the mid-term course, so has potential for bone fixation without the use of metal plates.

Multiple trauma complicated by traumatic vertebral artery injury without cervical vertebral injury: A case report.

Background: Blunt traumatic vertebral artery injury is commonly associated with head and cervical spinal trauma. However, those associated with chest or upper extremity injuries without cervical spine-related trauma are rare. Case presentation: A 94-year-old woman was injured in a motor vehicle crash. She was diagnosed with traumatic subarachnoid hemorrhage, bilateral subdural hematomas, right vertebral artery injury, and right clavicle fracture. No cervical spine injuries were observed. It was possible that the fracture fragment of the right clavicle may have directly injured the right vertebral artery. Coil embolization was performed for the vertebral artery injury. The patient had a good postoperative course and was transferred to the hospital for rehabilitation on day 65. Conclusion: Regarding the high-risk injury mechanism, blunt traumatic vertebral artery injuries in the V1-2 segment may occur in cases with clavicle fractures.

RAB35 is required for murine hippocampal development and functions by regulating neuronal cell distribution.

RAB35 is a multifunctional small GTPase that regulates endocytic recycling, cytoskeletal rearrangement, and cytokinesis. However, its physiological functions in mammalian development remain unclear. Here, we generated Rab35-knockout mice and found that RAB35 is essential for early embryogenesis. Interestingly, brain-specific Rab35-knockout mice displayed severe defects in hippocampal lamination owing to impaired distribution of pyramidal neurons, although defects in cerebral cortex formation were not evident. In addition, Rab35-knockout mice exhibited defects in spatial memory and anxiety-related behaviors. Quantitative proteomics indicated that the loss of RAB35 significantly affected the levels of other RAB proteins associated with endocytic trafficking, as well as some neural cell adhesion molecules, such as contactin-2. Collectively, our findings revealed that RAB35 is required for precise neuronal distribution in the developing hippocampus by regulating the expression of cell adhesion molecules, thereby influencing spatial memory.

Mice lacking doublecortin and doublecortin-like kinase 2 display altered hippocampal neuronal maturation and spontaneous seizures.

Mutations in doublecortin (DCX) are associated with intractable epilepsy in humans, due to a severe disorganization of the neocortex and hippocampus known as classical lissencephaly. However, the basis of the epilepsy in lissencephaly remains unclear. To address potential functional redundancy with murin Dcx, we targeted one of the closest homologues, doublecortin-like kinase 2 (Dclk2). Here, we report that Dcx; Dclk2-null mice display frequent spontaneous seizures that originate in the hippocampus, with most animals dying in the first few months of life. Elevated hippocampal expression of c-fos and loss of somatostatin-positive interneurons were identified, both known to correlate with epilepsy. Dcx and Dclk2 are coexpressed in developing hippocampus, and, in their absence, there is dosage-dependent disrupted hippocampal lamination associated with a cell-autonomous simplification of pyramidal dendritic arborizations leading to reduced inhibitory synaptic tone. These data suggest that hippocampal dysmaturation and insufficient receptive field for inhibitory input may underlie the epilepsy in lissencephaly, and suggest potential therapeutic strategies for controlling epilepsy in these patients.

Strategic neuronavigation-guided emergent endoscopic evacuation of the hematoma caused by ruptured brain arteriovenous malformation: Technical note and retrospective case series.

The treatment strategy for ruptured brain arteriovenous malformations (bAVMs) in the acute phase is still controversial. We describe five consecutive cases of successful emergent endoscopic evacuation (EEE) of intracerebral hematoma (ICH) caused by ruptured bAVMs with the electromagnetic (EM)-neuronavigation system to avoid damage to the bAVMs intended to save valuable time in the emergent phase. A single-institution retrospective analysis was performed in patients with ruptured bAVMs treated by the EM-navigated EEE as part of the strategic multimodality therapy. EM-navigated EEE was performed as follows: 1) obtaining three-dimensional computed tomography to identify the location of the nidus, large draining vein, feeding artery, and hematoma; 2) using a supine position without rigid head fixation for both supra- and infratentorial hematoma; 3) planning the entry point and trajectory of the endoscope as far as possible from the location of the nidus using the EM-navigation system; 4) designing a linear skin incision line suitable for the endoscopic surgery as well as possible decompressive craniectomy; and 5) performing EM-navigated endoscopic partial evacuation of ICH. EM-navigated EEE of ICH was successfully performed for all 5 patients, resulting in partial removal of the ICH without rebleeding from bAVMs. The mean surgical time was 37 min. Subsequent strategic endovascular embolization and curative resection of bAVMs could be performed for all patients, achieving Glasgow Coma Scale score of 15. EM-navigated EEE of partial ICH may be valuable in the emergent phase of ruptured bAVMs with massive life-threatening ICH to reduce the intracranial pressure and to obtain better prognosis.

Endoscope-integrated indocyanine green video angiography and the detection of the fragile periventricular collaterals associated with moyamoya disease: illustrative cases.

BACKGROUND: Hemorrhagic moyamoya disease (MMD) and the fragile periventricular collaterals are known to have a causal relationship. Digital subtraction angiography and magnetic resonance angiography have shown the presence of fragile periventricular moyamoya vessels. However, dynamic fragile periventricular moyamoya vessels have never been observed under direct vision. OBSERVATIONS: The authors treated two patients with hemorrhagic MMD: a 42-year-old man with intraventricular hemorrhage and a 47-year-old woman with intracerebral hemorrhage. Endoscope-integrated indocyanine green video angiography (EICG angiography) could visualize the dynamic fragile periventricular collaterals. In particular, EICG angiography enabled visualization of invisible moyamoya vessels buried in the subependyma and characterization of the blood flow in the moyamoya vessels located inside the lateral ventricles and hematoma cavity. LESSONS: EICG angiography can confirm the fragile periventricular collaterals associated with MMD by direct visualization. The high spatial resolution and real-time imaging can help to avoid accidental hemorrhage in and after evacuation of hemorrhage in patients with MMD.

Relationship between subarachnoid hemorrhage and nonocclusive mesenteric ischemia as a fatal complication: patient series.

BACKGROUND: Nonocclusive mesenteric ischemia (NOMI) causes intestinal necrosis due to irreversible ischemia of the intestinal tract. The authors evaluated the incidence of NOMI in patients with subarachnoid hemorrhage (SAH) due to ruptured aneurysms, and they present the clinical characteristics and describe the outcomes to emphasize the importance of recognizing NOMI. OBSERVATIONS: Overall, 7 of 276 consecutive patients with SAH developed NOMI. Their average age was 71 years, and 5 patients were men. Hunt and Kosnik grades were as follows: grade II, 2 patients; grade III, 3 patients; grade IV, 1 patient; and grade V, 1 patient. Fisher grades were as follows: grade 1, 1 patient; grade 2, 1 patient; and grade 3, 5 patients. Three patients were treated with endovascular coiling, 3 with microsurgical clipping, and 1 with conservative management. Five patients had abdominal symptoms prior to the confirmed diagnosis of NOMI. Four patients fell into shock. Two patients required emergent laparotomy followed by second-look surgery. Four patients could be managed conservatively. The overall mortality of patients with NOMI complication was 29% (2 of 7 cases). LESSONS: NOMI had a high mortality rate. Neurosurgeons should recognize that NOMI can occur as a fatal complication after SAH.

Using a Carpenter's Square to Localize Narrow or Multilayered Chronic Subdural Hematomas Diagnosed on Computed Tomography.

BACKGROUND: Chronic subdural hematomas (CSDHs) with narrow or multilayered hematomas must be accurately localized for burr hole drainage. We present a simple alternative localization method using conventional computed tomography (CT) scans acquired for the initial diagnosis and a commercially available carpenter's square (CS). METHODS: Using our novel method, we localized 77 narrow or multilayered CSDHs. A single burr hole site on the thickest portion of narrow hematomas or on the site allowing access to both the isolated superficial layer and the deep layer of multilayered hematomas was identified on axial CT images; the image was parallel to the orbitomeatal line (OML). On the target CT slice, the level from the OML and from the surface of the forehead to the intended burr hole (sagittal distance) was measured. The OML and the level of the CT target slice were marked using the CS. Then, the CS was placed at the marked target level; the 2 edges of the CS were situated on the frontal and temporal scalp and parallel to the OML and the sagittal line. The sagittal distance was then marked. RESULTS: All burr holes reached the CSDHs. The mean deviation of the burr holes was 4.7 mm inferior and 1.4 mm anterior to the intended site. In 65 instances (84.4%), a deviation within 10 mm was observed in both the superoinferior and the anteroposterior directions. CONCLUSIONS: Our simple and inexpensive method can localize narrow or multilayered CSDHs with acceptable accuracy and increases the efficiency of routine clinical work.