Olivary body exposure through far lateral and lower retrosigmoid approaches. Comparative analysis of the exposed surface and angle of attack.

OBJECTIVES: Throughout neurosurgical history, the treatment of intrinsic lesions located in the brainstem has been subject of much controversy. The brainstem is the anatomical structure of the central nervous system (CNS) that presents the highest concentration of nuclei and fibers, and its simple manipulation can lead to significant morbidity and mortality. Once one of the safe entry points at the medulla oblongata has been established, we wanted to evaluate the safest approach to the olivary body (the most used safe entry zone on the anterolateral surface of the medulla oblongata). The proposed objective was to evaluate the working channel from the surface of each of the far lateral and retrosigmoid approaches to the olivary body: distances, angles of attack and channel content. MATERIAL AND METHODS: To complete this work, a total of 10 heads injected with red/blue silicone were used. A total of 40 approaches were made in the 10 heads used (20 retrosigmoid and 20 far lateral). After completing the anatomical study and obtaining the data referring to all the approaches performed, it was decided to expand the sample of this research study by using 30 high-definition magnetic resonance imaging of anonymous patients without cranial or cerebral pathology. The reference points used were the same ones defined in the anatomical study. After defining the working channels in each of the approaches, the working distances, angle of attack, exposed surface, and the number of neurovascular structures present in the central trajectory were analyzed. RESULTS: The distances to the cranial and medial region of the olivary body were 52.71 mm (SD 3.59) from the retrosigmoid approach and 27.94 mm (SD 3.99) from the far lateral; to the most basal region of the olivary body, the distances were 49.93 (SD 3.72) from the retrosigmoid approach and 18.1 mm (SD 2.5) from the far lateral. The angle of attack to the caudal region was 19.44° (SD 1.3) for the retrosigmoid approach and 50.97° (SD 8.01) for the far lateral approach; the angle of attack to the cranial region was 20.3° (SD 1.22) for the retrosigmoid and 39.9° (SD 5.12) for the far lateral. Regarding neurovascular structures, the probability of finding an arterial structure is higher for the lateral far, whereas a neural structure will be more likely from a retrosigmoid approach. CONCLUSIONS: As conclusions of this work, we can say that far lateral approach presents more favorable conditions for the microsurgical treatment of intrinsic bulbar and bulbomedullary lesions approached through the caudal half of the olivary body. In those cases of bulbar and pontine-bulbar lesions approached through the cranial half of the olivary body, the retrosigmoid approach can be considered for selected cases.

Midline Suboccipital Unilateral Trans-Cerebellomedullary Fissure Approach for Clipping of Ruptured VA-PICA Aneurysm: Two-Dimensional Operative Video.

The vertebral artery-posterior inferior cerebellar artery (VA-PICA) aneurysm poses a technical challenge for microsurgical clipping due to its anatomical complexity, which requires dissection of lower cranial nerves. Endovascular treatment is regarded as a feasible first-line therapeutic option for VA-PICA aneurysm because it has an acceptable aneurysm occlusion rate and is less invasive. However, microsurgical clipping remains an effective treatment option. We present the case of a 62-year-old man who presented with subarachnoid hemorrhage (SAH) due to a ruptured VA-PICA aneurysm. Neuroradiologic examination revealed a 2-3 mm medially pointing left VA-PICA aneurysm with acute obstructive hydrocephalus due to massive SAH in the posterior cranial fossa. As the patient had acute obstructive hydrocephalus and a relatively small aneurysm, we selected clipping over endovascular treatment. Because the aneurysm was located close to the midline and anterolateral to the medulla oblongata, we approached it from the midline. A midline suboccipital craniotomy, C1 laminectomy, and drilling of the left condylar fossa were performed; a unilateral cerebellomedullary fissure opening was added; and the aneurysm was clipped. Postoperative neuroradiologic examinations revealed complete obliteration of the aneurysm. As shown in this video, unilateral cerebellomedullary fissure opening combined with adequate removal of the condylar fossa provides a wide operative field in the cerebellomedullary cistern while avoiding strong retraction of the cerebellum. We believe that this technique makes VA-PICA aneurysm clipping safe and successful. Patient consent was obtained to perform the surgery and to publish the surgical video (Video 1).

Highest resolution microCT scan of the human brainstem reveals putative anatomical basis for infrequency of medial medullary syndrome.

Ischemic strokes affecting the medial medulla are exceedingly rare. The anatomical basis for the relative infrequency of this stroke syndrome has been largely uninvestigated due to historically coarse MRI and CT scan resolution. We capture and digitally dissect the highest-ever-resolution diffusible iodine-based contrast-enhanced CT (diceCT) scanned images of a cadaveric brainstem to map arterial territories implicated in medial medullary infarctions. 3D reconstructions show that within the anterior spinal artery territory previously implicated in medial medullary syndrome (MMS), there are numerous, small sulcal artery branches perforating the medulla within the anterior median fissure. These branches proceed in parallel through the anteroposterior depth of the medulla as expected; however, we also identify a network of intraparenchymal, rostrocaudal anastomoses between these sulcal perforating branches. This network of intraparenchymal sulcal artery anastomoses has never been described and may provide a significant collateral supply of oxygenated blood flow throughout the medial medulla. By ramifying deeper tissues, these anastomoses can help explain the infrequency of MMS.

Vertebral artery dissection induced lateral medullary syndrome characterized with severe bradycardia: a case report and review of the literature.

BACKGROUND: Lateral medullary syndrome is the most common type of brainstem infarction. Lateral medullary syndrome results in damage to the corresponding cranial nerve nuclei and the nucleus tractus solitarius, with vertigo, ipsilateral ataxia, crossed sensory disturbances, Horner's sign, bulbar palsy, and other underlying symptoms or signs. However, cases with cardiac arrhythmia and other autonomic dysfunctions as the primary manifestations are less common. Clinically, sudden death occasionally occurs in patients with lateral medullary syndrome, which may be associated with severe cardiac arrhythmia. These patients may suffer in life-threatening arrhythmia and even cardiac arrest, and vital signs should be closely monitored to prevent sudden death. In younger patients, vertebral artery dissection is the most common cause. CASE DESCRIPTION: Here, we present a case of lateral medullary syndrome caused by vertebral artery dissection with severe bradycardia. The patient was a 49-year-old man who was admitted with "sudden onset of numbness in the left limbs and right side of the face for 1 hour". Electrocardiogram (ECG) monitoring showed a repeated heart rate decrease to as low as 23 beats/min, followed by a gradual increase in heart rate to 35-55 beats/min after 2-3 seconds. Head magnetic resonance imaging (MRI) examination revealed right dorsolateral cerebral infarction of the medulla oblongata. Digital subtraction angiography (DSA) revealed a right vertebral artery dissecting aneurysm. We performed an emergency placement of a temporary pacemaker, followed by conservative treatment with platelet aggregation inhibitors, vascular softening agents and improved collateral circulation. Elective spring coil embolization of the vertebral artery dissecting aneurysm and stent implantation were performed. At outpatient follow-up, the patient had a good prognosis. CONCLUSIONS: Clinical management of patients with lateral medullary syndrome should be prioritized, with close cardiac monitoring at the early stages of observation and pacemaker placement and tracheal intubation as required to prevent adverse events.

Anatomic and MRI bases for medullary infarctions with patients' presentation.

OBJECTIVE: There is a low incidence of the medullary infarctions and sparse data about the vascular territories, as well as a correlation among the anatomic, magnetic resonance imaging (MRI) and neurologic signs. MATERIALS AND METHODS: Arteries of the 10 right and left sides of the brain stem were injected with India ink, fixed in formalin and microdissected. The enrolled 34 patients with medullary infarctions underwent a neurologic, MRI and Doppler examination. RESULTS: Four types of the infarctions were distinguished according to the involved vascular territories. The isolated medial medullary infarctions (MMIs) were present in 14.7%. The complete MMIs comprised one bilateral infarction (2.9%), whilst the incomplete and partial MMIs were observed in 5.9% and 8.9%, respectively. The anterolateral infarctions (ALMIs) were very rare (2.9%). The complete and incomplete lateral infarctions (LMIs), noted in 35.3%, comprised 11.8% and 23.6%, respectively, that is, the anterior (5.9%), posterior (8.9%), deep (2.9%), and peripheral (5.9%). Dorsal ischemic lesions (DMIs) occurred in 11.8%, either as a complete (2.9%), or isolated lateral (5.9%) or medial infarctions (2.9%). The remaining ischemic regions belonged to various combined infarctions of the MMI, ALMI, LMI and DMI (35.3%). The infarctions most often affected the upper medulla (47.1%), middle (11.8%), or both (29.5%). Several motor and sensory signs were manifested following infarctions, including vestibular, cerebellar, ocular, sympathetic, respiratory and auditory symptoms. CONCLUSIONS: There was a good correlation among the vascular territories, MRI ischemia features, and neurologic findings regarding the medullary infarctions.

Severe Unilateral Proprioceptive Loss in Medullary- Rostral Spinal Cord Infarction. A Posterior Spinal Artery Syndrome.

We draw attention to a unique presentation, severe unilateral loss of limb proprioception, in patients with medullary and rostral spinal cord infarction. Two patients developed acute severe proprioceptive loss in the limbs ipsilateral to infarcts that involved the caudal medulla and rostral spinal cord. They also had symptoms and signs often found in lateral medullary infarction. The proprioceptive loss is attributable to injury to the gracile and cuneate nuclei and/or their projections to the medial lemniscus. The infarct territory is supplied by the posterior spinal branches of the vertebral artery near its penetration into the posterior fossa. The presence of severe ipsilateral proprioceptive loss in a patient with features of lateral medullary infarction indicates involvement of the rostral spinal cord.

Anatomical Study of the Posterior Spinal Artery Branches to the Medulla Oblongata.

BACKGROUND: The posterior spinal arteries (PSAs), branches of the intracranial segment of the vertebral artery or posterior inferior cerebellar artery, run bilaterally along the spinal cord and are integral to the blood supply primarily to the posterior one third of this structure. However, a less well-described distribution of the PSAs is their supply to the posterior medulla. The purpose of this study is to examine the medullary branches of the PSA anatomically. METHODS: We conducted a cadaveric study to evaluate for branches of the PSA supplying the medulla oblongata. RESULTS: All 14 sides had medullary branches arising from the PSAs. The average number of branches supplying the medulla oblongata on each side was 6. Most of these branches traveled laterally to anastomose with medullary branches arising from the anterior spinal artery. Additionally, lateral and ascending branches were noted. CONCLUSIONS: Physicians who interpret imaging of the craniocervical junction, in particular arteriograms, should be aware of ascending medullary branches arising from the anterior spinal artery. Additionally, neurosurgeons operating this region must be careful in dissecting over the posterior medulla and manipulating the cerebellar tonsils, as in telovelar approaches to the fourth ventricle, in order to avoid iatrogenic injury to these vessels. Additionally, variable stroke patterns involving the vertebral artery or posterior inferior cerebellar artery might include ischemia to the medulla oblongata via PSA branches, and this anatomy should be kept in mind by interventionalists, radiologists, and neurologists alike.

Predictors of Outcome in Patients with Medullary Hemorrhage.

BACKGROUND: Isolated medullary hemorrhage (MH) is an uncommon presentation of spontaneous intraparenchymal hemorrhage. The relationship between MH and neurological outcome is not well known. This study aims to assess predictive parameters for the outcome of medullary hemorrhage. METHODS: We conducted an extensive search of the literature for cases with spontaneous, isolated MH. The study was conducted according to the statement of Preferred Reporting Items for Systematic Reviews and Meta Analysis (PRISMA). Forty-three cases diagnosed by CT or MRI have been reported in the literature, to which we add three confirmed by MRI. The ventrodorsal size of hemorrhage was taken into account as a parameter of outcome. Early neurologic deterioration (END) was defined as an incremental increase in the National Institutes of Health Stroke Scale score by ≥1 point in motor power, or ≥2 points in the total score within the first week after admission. Modified Rankin Score (mRS) 0-2 was presumed as favorable outcome (FO) and mRS 3-6 score as unfavorable outcome (UO) at discharge and at 3 months after stroke. RESULTS: We enrolled 46 patients, and 17 (37%) patients were diagnosed with END. The cause of medullary hemorrhage was mostly vascular malformations, including cavernous malformation (33%) and arteriovenous malformation (11%). In univariate analyses, neither arteriovenous malformations (OR, 1.04; 95%CI, 0.10-10.53; P = 0.68) nor cavernomas (OR, 1.04; 95%CI, 0.22-4.89; P = 0.62) were associated with UO. Acute respiratory distress syndrome was higher in patients with UO group (44%) compared to those with FO group (16%), but this difference did not reach to a significant level (OR, 4.13; 95%CI, 0.85-20.04; P = 0.09). The diameter of hemorrhage was significantly larger (≥1 cm) in patients with UO compared to those with FO (OR, 16.67; 95%CI, 1.87-148.89; P = 0.003). Three months after stroke, 37 patients (80%) had FO and 9 (19.5%) had UO, and 5 (11%) died. Multiple logistic regression analysis using predetermined variables found to be significant in univariate analyses (END, consciousness disturbance at admission, hemorrhage size, and hypertension) showed that END at stroke onset was significantly associated with UO (OR, 4.97; CI95%, 1.13-21.94; P = 0.03). CONCLUSIONS: These results suggest that the END is a predictor for UO in patients with medullary hemorrhage. The extent of the medullary hemorrhage along the conduction tract may contribute to deterioration.

Asymmetry of medullary veins on multiphase CT-angiography in patients with acute ischemic stroke.

BACKGROUND: It was previously demonstrated that decreased cortical venous drainage is a predictive factor of poor clinical outcome in patients with an acute ischemic stroke. The aim of this investigation is to test the hypothesis that the decline in blood flow in medullary veins (MV) on CT angiogram (CTA) of patients with acute ischemic stroke (AIS) can also be predictive of clinical outcome. METHODS: We retrospectively reviewed a database of patients with AIS who were evaluated by multiphase CTA and enrolled individuals with AIS and evidence of occlusion of the intracranial internal carotid artery, the M1 or M2 segment of the middle cerebral artery, or combination of two occlusions. To characterize asymmetry of MV we used similar principle that was previously established for MV on SWI MR-images; asymmetry was defined was presence of 5 or more contrast opacified MV in one hemisphere as compared to the contralateral side. Clinical outcomes were evaluated by mRS in 90 days. The Fisher Exact test was used to examine the significance of the MV asymmetry. Odds ratio and interrater variability were calculated. RESULTS: 66 patients with AIS were included. The presence of asymmetry in MV was associated with the higher frequency of poor clinical outcomes (84.6% vs 50.9%); the OR was 5.3. Interrater agreement in assessment on MV was moderate in our study (κ=0.55). CONCLUSION: This study shows that (a) medullary veins can be reliably assessed on multiphase CTA, (b) in patients with AIS, asymmetric appearance of MV is associated with poor clinical outcome.

Isolated Infarction of the Medullary Pyramid - A Rare Pure Motor Stroke.

Acute pure motor hemiparesis can occur due to a vascular insult along the cortico spinal pathway. Rarely such a stroke can occur as a result of involvement of the pyramids located on the ventral aspect of the medulla. Neurological localization can be difficult in such strokes and moreover they can also pose imaging challenges since they are missed on the CT scans. So far only 4 such cases have been reported in literature. Here we present two cases of pure motor strokes caused by infarction of the medullary pyramids. We have described the anatomical correlates of the symptoms and signs and also highlight the importance of MRI in picking up these rare strokes.

[Hemiplegia cruciata and severe facial pain due to infarction of the cervicomedullary junction: a case report].

We report the case of a 66-year-old female with hemiplegia cruciata and severe facial pain due to infarction of the cervicomedullary junction. She presented to the hospital with complaints of acute-onset left facial pain and gait disturbance. Neurological examination revealed narrow left palpebral fissure, severe left facial pain and hypothermoesthesia, weakness predominantly in the left upper and right lower extremities, decreased pain and temperature sensation in the right lower extremity, decreased vibration sensation in the left lower extremity, hyperreflexia in the left upper extremity, and mild ataxia in the left upper and lower extremities. Brain MRI revealed a high-intensity lesion in the left cervicomedullary junction on diffusion-weighted and fluid-attenuated inversion recovery images. Hemiplegia cruciata due to the pyramidal tract injury at the cervicomedullary junction is an uncommon clinical manifestation. However, in patients with hemiplegia cruciata, identifying the lesion location may be difficult. Clinicians should consider the possibility of pyramidal decussation lesions. Anatomical differences, in the course of pyramidal tract fibers between the upper and lower limbs have been considered in the pyramidal decussation. Hemiplegia cruciata in this case was primarily caused by the impairment of the left upper limb pyramidal fibers after the pyramidal decussation and the right lower limb pyramidal fibers before the pyramidal decussation.

Neuroanatomical basis of Wallenberg syndrome.

Wallenberg syndrome, or lateral medullar syndrome, is the clinical presentation of the infarct in the territory of posterior inferior cerebellar artery. Its signs and symptoms include vertigo, nystagmus, diplopia, ipsilateral Horner syndrome, facial ruddiness and dry skin, dysphonia, dysphagia, dysarthria, ipsilateral loss of gag reflex, ipsilateral ataxia, ipsilateral impaired taste, ipsilateral facial pain and paresthesia, decreased ipsilateral blink reflex, contralateral hypoalgesia and thermoanaesthesia in the trunk and limbs; and ipsilateral facial hypoalgesia and thermoanaesthesia. Neuroanatomical knowledge is essential to its comprehension, study and diagnosis, because the classic neurological manifestations are easy to explain and understand if function and localization of affected anatomical structures are known as if the posterior cerebral circulation is.

El síndrome de Wallenberg, o síndrome bulbar lateral, es la manifestación clínica del infarto en el territorio de irrigación de la arteria cerebelosa posteroinferior. Su presentación incluye vértigo, nistagmo, diplopía, síndrome de Horner, rubicundez y anhidrosis facial homolateral, disfonía, disfagia, disartria, pérdida homolateral del reflejo nauseoso, ataxia homolateral, disgeusia homolateral, dolor y parestesia faciales homolaterales, pérdida o disminución homolateral del reflejo corneal, hipoalgesia y termoanestesia de tronco y extremidades contralaterales, hipoalgesia y termoanestesia facial homolateral. El conocimiento neuroanatómico es imprescindible para su comprensión, estudio y diagnóstico, ya que sus manifestaciones neurológicas clásicas son fácilmente explicables y entendibles si se conocen la función y la localización de las estructuras anatómicas afectadas, así como la irrigación cerebral posterior.

[A case of bilateral medial medullary and left tegmentum of pontine infarction in whom DSA-MR fusion imaging identified infarct-relevant arteries].

We herein reported a patient with acute ischemic stroke in the bilateral medial medullary and the left tegmentum of the pons who presented with various neurological symptoms. Fusing digital subtraction angiography (DSA) and MRI (DSA-MR fusion imaging) could reveal the infarct-relevant arteries. A 41-year-old male presented with headache, bilateral arm's dysesthesia, quadriplegia, left Horner's syndrome, upbeat nystagmus, internuclear ophthalmoplegia and left peripheral facial paralysis. Diffusion weighted MRI (DWI) revealed the high intensity lesion in the bilateral medial medullary and the left tegmentum of the pons. MRA showed right vertebral artery (VA) occlusion. A high intensity on T1 weighted imaging was shown on the right VA vessel wall. DSA-MR fusion imaging revealed the anterior spinal artery (ASA) occlusion proximal to the infarction. The stenosis was located at the origin of the right VA perforating branch distributing into the infarct lesion. The steno-occlusive lesion of ASA and VA perforating branch due to VA dissection resulted in infarction in the pontomedullary junction and caused various neurological symptoms. DSA-MR fusion imaging would prove the radiological anatomy of infarct-relevant arteries and clarify the etiology of ischemic stroke.

Medullary Infarction Leading to Locked-In Syndrome Following Lumbar Puncture in a Patient with Basilar Invagination.

BACKGROUND: Lumbar puncture is a common procedure that can be safely performed in most patients. Certain populations may have increased risk for complications following lumbar puncture, but the significance of basilar invagination is often underappreciated. CASE DESCRIPTION: A 45-year-old woman with basilar invagination received multiple lumbar punctures in the workup of acute meningitis. Preprocedural computed tomography was obtained. Following lumbar puncture, the patient developed locked-in syndrome. Magnetic resonance imaging obtained several days later demonstrated severe compression and infarction of the medulla and inferior cerebellum by the odontoid process and ectopic cerebellar tonsils. The patient was transferred but at this point, surgical decompression was not possible. She did not regain significant neurologic function. CONCLUSIONS: Basilar invagination is a risk factor for devastating neurologic complications following lumbar puncture. Awareness of this complication and prompt recognition of its occurrence may prevent future morbidity of lumbar puncture in patients with basilar invagination.

Organ blood flow in response to infusion of arginine vasopressin in premature fetal sheep.

BACKGROUND: Arginine vasopressin (AVP) infusion has been shown to be a useful strategy for the management of systemic perfusion failure in premature infants. Our objective was to determine the characteristics of the blood flow redistribution induced by AVP infusion in premature fetal sheep. METHODS: Nine sheep fetuses at 99 to 113 days of gestation were continuously infused with AVP. Measurement of blood flow to individual fetal organs was performed using a colored microsphere technique, with measurements performed at 30 min before and 90 min after the initiation of AVP infusions. RESULTS: The AVP infusion significantly increased blood flow to the medulla oblongata (P < 0.05), and significantly decreased flow to the adrenal glands (from 492.0 ± 239.6 to 364.9 ± 143.3 mL/min/100 g, P < 0.05) and heart (from 592.6 ± 184.5 to 435.6 ± 137.4 mL/min/100 g, P < 0.05). The infusion significantly increased the vascular resistance in adrenal glands, kidneys, ileum, colon, heart, and cerebellum. In the brain, except for the cerebellum, no significant increase in resistance was identified. CONCLUSIONS: There was no significant response to AVP infusion in cerebral blood flow in mid-gestation fetal sheep. Our observations suggest that, under AVP stimulation, the blood flow to the adrenal glands and myocardium might be decreased due to an increase in vascular resistance.

Anatomical relationships between medullary veins and three types of deep-seated malignant brain tumors as detected by susceptibility-weighted imaging.

BACKGROUND: Deep-seated brain tumors can be difficult to differentiate. Three tumor types (primary central nervous system lymphoma [PCNSL], high-grade glioma, and metastatic brain tumors), identified by susceptibility-weighted imaging, have different relationships with small medullary veins, and these relationships can be used to enhance diagnostic accuracy. METHODS: Records of patients with pathology confirmed malignant brain tumors who received susceptibility-weighted imaging between 2009 and 2015 were reviewed. A total of 29 patients with deep-seated malignant brain tumors in the territory of small medullary veins were enrolled in this study. The sensitivity, specificity, and diagnostic accuracy of medullary vein blockage (MVB), defined as a small medullary vein terminating at the margin of the tumor, for indicating malignant brain tumors were analyzed. RESULTS: Of 11 patients with PCNSLs, 5 with high-grade gliomas, and 13 with metastases, only the latter presented MVBs. The sensitivity, specificity, and accuracy of using MVBs for diagnosing metastatic tumors were 76.9%, 100%, and 89.7%, respectively. CONCLUSION: An MVB is an accurate sign for differentiating metastatic brain tumors from two other common malignancies and thus provides a useful tool for preoperative planning.

Medullary Compression Due to Ectatic Vertebral Artery-Case Report and Review of Literature.

Medullary compression syndrome due to anomalous course of blood vessels is a rare disease most commonly seen in the adult population. The offending vessels causing this syndrome are mostly posterior inferior cerebellar artery or the vertebral artery. The symptoms of this syndrome vary from most common hypertension to various other neurologic deficits like hemiplegia, dysesthesia, and dysarthria. Intractable dizziness is a rare symptom of this disease. The definite management plan for this disease is microvascular decompression. We present our case of medullary compression syndrome which manifested as intractable dizziness. We describe our experience in the management of this patient as well as present a review of literature of this rare disease.