Medullary branches of the vertebral artery: microsurgical anatomy and clinical significance.

BACKGROUND: Since the medullary arteries are of a great neurologic and neurosurgical significance, the aim was to perform a detailed microanatomic study of these vessels, as well as of the medullary infarctions in a group of patients. METHODS: The arteries of 26 halves of the brain stem were injected with India ink and gelatin, microdissected and measured with an ocular micrometer. Neurologic and magnetic resonance imaging (MRI) examinations were performed in 11 patients. RESULTS: The perforating medullary arteries, averaging 6.7 in number and 0.26 mm in diameter, most often originated from the anterior spinal artery (ASA), and rarely from the vertebral (VA) (38.5%) and the basilar artery (BA) (11.6%). They supplied the medial medullary region. The anterolateral arteries, 4.8 in number and 0.2 mm in size, most often arose from the ASA and PerfAs, and nourished the anterolateral region. The lateral arteries, 2.2 in number and 0.31 mm in diameter, usually originated from the VA and the posterior inferior cerebellar artery (PICA). They supplied the lateral medullary region. The dorsal arteries, which mainly arose from the PICA and the posterior spinal artery (PSA), nourished the dorsal region, including the roof of the 4th ventricle. The anastomotic channels, averaging 0.3 mm in size, were noted in 42.3%. Among the medullary infarctions, the lateral ones were most frequently present (72.8%). CONCLUSION: The obtained anatomic data, which can explain the medullary infarctions symptomatology, are also important in order to avoid damage to the medullary arteries during neurosurgical and neuroradiologic interventions.

Successful microvascular decompression surgery for dolichoectatic vertebral artery compression of medulla oblongata in a patient with hypersomnia disorder.

INTRODUCTION: Hypersomnia is a condition in which a person has trouble staying awake during the day. There are several potential causes of it, including sleep apnea and sleep disorders. CASE PRESENTATION: A 43 year old male was referred to our practice with complaints of hypersomnia, snoring, slurred speech and sleep apnea for more diagnostic and therapeutic interventions. His brain MRI was significant for a vascular loop compression on medulla oblongata. The patient underwent microvascular decompression surgery subsequently and showed improvement in all of his symptoms. CONCLUSION: One of the rare causes of sleep apnea is medulla oblongata compression by a vascular loop. Vertebrobasilar dolichoectasia may cause this phenomenon probably and should be reviewed in imaging examinations more precisely. Microvascular decompression by using a synthetic Teflon patch may be helpful in management of these patients.

Microsurgical anatomy of safe entry zones on the ventrolateral brainstem: a morphometric study.

Surgery of the brainstem is challenging due to the complexity of the area with cranial nerve nuclei, reticular formation, and ascending and descending fibers. Safe entry zones are required to reach the intrinsic lesions of the brainstem. The aim of this study was to provide detailed measurements for anatomical landmark zones of the ventrolateral surface of the human brainstem related to previously described safe entry zones. In this study, 53 complete and 34 midsagittal brainstems were measured using a stainless caliper with an accuracy of 0.01 mm. The distance between the pontomesencephalic and bulbopontine sulci was measured as 26.94 mm. Basilar sulcus-lateral side of pons (origin of the fibers of the trigeminal nerve) distance was 17.23 mm, transverse length of the pyramid 5.42 mm, and vertical length of the pyramid 21.36 mm. Lateral mesencephalic sulcus was 12.73 mm, distance of the lateral mesencephalic sulcus to the oculomotor nerve 13.85 mm, and distance of trigeminal nerve to the upper tip of pyramid 17.58 mm. The transverse length for the inferior olive at midpoint and vertical length were measured as 5.21 mm and 14.77 mm, consequently. The thickness of the superior colliculus was 4.36 mm, and the inferior colliculus 5.06 mm; length of the tectum was 14.5 mm and interpeduncular fossa 11.26 mm. Profound anatomical knowledge and careful analysis of preoperative imaging are mandatory before surgery of the brainstem lesions. The results presented in this study will serve neurosurgeons operating in the brainstem region.

Evolution of cerebellomedullary fissure opening: its effects on posterior fossa surgeries from the fourth ventricle to the brainstem.

Surgical approaches to the fourth ventricle and its surrounding brainstem regions have changed significantly in the previous 30 years, after the establishment of cerebellomedullary fissure (CMF) opening. With the development of CMF opening techniques, CMF opening surgeries have become widely used for the treatment of various pathologies and have contributed to the improvement of surgical results in posterior fossa surgeries. We here review the historical progress of CMF opening surgeries to help the future progression of neurosurgical treatments. The authors studied the available literature to clarify how CMF opening surgeries have developed and progressed, and how much the idea and development of CMF opening techniques have affected the advancement of posterior fossa surgeries. With the establishment of angiography, anatomical studies on CMF in the 1960s were performed mainly to clarify vascular anatomy on radiological images. After reporting the microsurgical anatomy of CMF in a cadaveric study in 1982, one of the authors (T.M.) first proposed the clinical usefulness of CMF opening in 1992. This new method enabled wide exposure of the fourth ventricle without causing vermian splitting syndrome, and it took the place of the standard approach instead of the conventional transvermian approach. Several authors reported their experiences using this method from the end of the twentieth century to the early twenty-first century, and the naming of the approach, "telovelar approach" by Mussi and Rhoton in 2000 contributed to the global spread of CMF opening surgeries. The approach has become widely applied not only for tumors but also for vascular and brainstem lesions, and has assisted in the development of their surgical treatments, and brought up the idea of various fissure dissection in the posterior fossa. Studies of microsurgical anatomy of the fourth ventricle, including the CMF, has led to new surgical approaches represented by the transCMF/telovelar approach. The CMF opening method caused a revolution in posterior fossa surgeries. The idea was developed based on the experience gained while dissecting the CMF (the roof of the fourth ventricle) in the laboratory. Anatomical studies using cadaveric specimens, particularly their dissection by surgeons themselves, together with a deep understanding of brain anatomy are essential for further advancements in neurosurgical treatments.

Stereotactic posterior midline approach under direct microscopic view for biopsy of medulla oblongata tumors: technical considerations.

BACKGROUND: Open and stereotactic transfrontal or transcerebellar approaches have been used to biopsy brainstem lesions. METHOD: In this report, a stereotactic posterior and midline approach to the distal medulla oblongata under microscopic view is described. The potential advantages and limitations are discussed, especially bilateral damage of the X nerve nuclei. CONCLUSION: This approach should be considered for biopsy of distal and posterior lesions. We strongly recommend the use of direct microscopic view to identify the medullary vessels, confirm the midline entry point, and avoid potential shift of the medulla. Further experience is needed to confirm safety and success rate of this approach.

Rare occurrence of gangliocytoma in the medulla oblongata.

Gangliocytoma is an uncommon low-grade neuroepithelial tumour arising in the cerebral hemispheres, with medulla oblongata being extremely rare site of occurrence. We report a case of an 8-year-old female with recurrent vomiting, hypertension and left hemifacial spasms with a dorsally exophytic lesion arising from the medulla projecting into the fourth ventricle. She underwent excision of the lesion with intra operative cranial nerve monitoring guidance. Histopathology revealed clusters of large mature ganglion cells which were labelled by synaptophysin and CD34. Extreme rarity in this location makes clinical diagnosis and management of gangliocytoma challenging, although prompt diagnosis and total excision has a successful outcome. There are only six previous reports of gangliocytoma in the medulla oblongata.

Complex Cervicomedullary Junction Malformation and Hypoplastic Cerebellar Tonsils following Fetal Repair of Myelomeningocele: Case Report and Literature Review.

BACKGROUND: Following the publication of the Management of Myelomeningocele study (MOMS), fetal repair of myelomeningocele (MMC) has become increasingly prevalent worldwide. However, limited case presentations exist illustrating the potential mechanical and embryological effects of fetal repair. We present a unique case report of a complex embryological cervicomedullary junction (CMJ) malformation and cerebellar hypoplasia following fetal repair of MMC. CASE DESCRIPTION: A 1-day-old female was referred to the paediatric neurosurgical team after having successful surgical intrauterine closure of MMC abroad at 25 weeks gestation. The patient was born by emergency caesarean section at 33 weeks gestation and had a ventricular-peritoneal shunt inserted at 25 days old due to resulting hydrocephalus. Neonatal MRI scans revealed a complex number of malformations that included a split cord located at the CMJ, hypoplasia of the cerebellum and vermis, and a Chiari type II malformation. CONCLUSION: It is possible that the clefting of the upper cervical spinal cord was undetected at preoperative MRI; however, this is unlikely given the antenatal images. It is our hypothesis that the malformation may have exhibited mechanical change after the repair, as the preoperative MRI showed only a Chiari II malformation without any of the complex abnormalities being present and the split cord was already there but not obvious. There are no existing reports of such a complex malformation following antenatal surgery in the literature. This should be further explored as more cases and trials become available.

Microvascular decompression for the treatment of neurogenic hypertension with trigeminal neuralgia.

BACKGROUND: To evaluate the efficacy of microvascular decompression (MVD) in reducing hypertension (HTN) in hypertensive patients with trigeminal neuralgia (TN). METHODS: The clinical data of 58 cases of neurogenic HTN with TN treated in our hospital were retrospectively reviewed. Preoperative MR revealed abnormal blood pressure in the left rostral ventrolateral medulla (RVLM) and the posterior cranial nerve root entry zone (REZ). The patients were divided into control group: only trigeminal nerve was treated with MVD; experimental group: trigeminal nerve, RVLM and REZ were treated with MVD at the same time. The patients were followed up for 6 months to 1 year to observe the changes of blood pressure. RESULTS: There was no significant difference in gender, age, course of TN, course of HTN, grade of HTN and preoperative blood pressure between the two groups. After operation, the effective rate of HTN improvement with MVD was 32.1% in the control group. There was no significant difference in the preoperative and post operative blood pressure. (P△SBP = 0.131; P△BDP = 0.078). In the experimental group, the effective rate was 83.3%. The postoperative blood pressure was significantly lower than preoperative values. (P△SBP < 0.001; P△DBP < 0.001). CONCLUSIONS: MVD is an effective treatment for neurogenic HTN. However, the criteria for selecting hypertensive patients who need MVD to control their HTN still needs to be further determined. Possible indications may include: left trigeminal neuralgia, neurogenic HTN; abnormal blood pressure compression in the left RVLM and REZ areas on MR; and blood pressure in these patients can not be effectively controlled by drugs.

Angular and metric analysis of the neural structures in the cerebellopontine angle.

INTRODUCTION: The cerebellopontine angle (CPA) is a subarachnoid space in the lateral aspect of the posterior fossa. In this study, we propose a complementary analysis of the CPA from the cerebellopontine fissure. METHODS: We studied 50 hemi-cerebelli in the laboratory of neuroanatomy and included a description of the CPA anatomy from the cerebellopontine fissure and its relationship with the flocculus and the 5th, 6th, 7th, and 8th cranial nerves (CN) origins. RESULTS: The average distance from the 5th CN to the mid-line (ML) was 19.2 mm, 6th CN to ML was 4.4 mm, 7-8 complex to ML was 15.8 mm, flocculus to ML was 20.5 mm, and flocculus to 5th CN was 11.5 mm, additionally, and the diameter of the flocculus was 9.0 mm. The angle between the vertex in the flocculus and the V CN and the medullary-pontine line was 64.8 degrees. DISCUSSION: The most common access to the CPA is through the retrosigmoid-suboccipital region and this approach can be done with the help of an endoscope. The anatomy of origins of neural structures tends to be preserved in cases of CPA lesions. CONCLUSION: Knowledge of the average distances between the neural structures in the cerebellar-pontine fissure and the angular relationships between these structures facilitates the use of surgical approaches such as microsurgery and endoscopy.

Intramedullary placement of ventricular shunts: a review of using bone as a distal cerebrospinal absorption site in treating hydrocephalus.

PURPOSE: Intraosseous (IO) vascular access has been used since the Second World War and is warranted when there is an emergency and/or urgent need to replenish the vascular pool. Despite long-term and satisfactory results from delivering large quantities of intravenous fluid via the medullary space of bone, use of this space for a distant receptacle for cerebrospinal fluid (CSF) diversion has seldom been considered. METHODS: The current paper reviews the literature regarding the bony medullary space as a receptacle for intravenous fluid and CSF. RESULTS: Previous authors have demonstrated the potential of the diploic space of the calvaria for CSF shunting. Pugh and colleagues tested the ability of the cranium to receive and absorb a small amount of tracer fluid. CONCLUSION: The literature suggests that intraosseous placement of ventricular diversionary shunts is an alternative to more traditional sites such as the pleural cavity and peritoneum. When these latter locations are not available or are contraindicated, placement in the medullary space of bone is another option available to the surgeon.

Vertebral artery dolicoectasia with brainstem compression: role of microvascular decompression in relieving pyramidal weakness.

Vertebral artery dolicoectasia (VAD) can cause brainstem compression and dysfunction. Reports of pyramidal tract involvement by brainstem compression and the surgical benefits and its long-term results are sparsely reported. We hereby report three cases of medullary compression by VAD causing pyramidal weakness. Two patients with bilateral compression with quadriparesis did not want surgical treatment and were still disabled at 58 months and 50 months of follow-up, respectively. One patient with unilateral medullary compression with hemiparesis underwent microvascular decompression using Teflon sling retraction. This patient was relieved of symptoms and is asymptomatic at 14-month follow-up. This report emphasizes the need of surgical decompression in cases of brainstem compression by VAD with caution about appropriate case selection.

A posttraumatic pontomedullary rent with good outcome.

Posttraumatic pontomedullary rents have been described mainly as postmortem histopathological findings in patients who died immediately or within the first hours after trauma. To the best of our knowledge, no long-term survivors of this condition have been described, and those surviving initially were always severely impaired. We present the first patient with this condition and with corresponding lesions on imaging who survived longer than 3 months. Moreover, the patient regained almost complete independence 1 year after the trauma. We briefly discuss the proposed mechanisms of this injury. We conclude that this lesion, when incomplete, is not always lethal and can exceptionally have a good clinical outcome. Prevention of respiratory failure is of utmost importance in these patients.

Surgical resection of medulla oblongata hemangioblastomas: outcome and complications.

OBJECT: The purpose of this study was to analyze the surgical outcome and complications of a single-center series of medulla oblongata (MO) hemangioblastomas. METHODS: We retrospectively reviewed the medical charts of all medulla oblongata hemangioblastomas operated on at our institution between 1996 and 2015. All patients had a pre- and postoperative MRI and a minimum follow-up of 6 months. Patients were scored according to the Karnofsky Performance Scale (KPS) and McCormick Scale at the moment of admission, discharge and the last follow-up. RESULTS: Thirty-one surgical procedures were performed on 27 patients (16 females and 11 males). The mean age was 33 years, and 93 % of patients had von Hippel Lindau (VHL) disease. Three patients experienced very complicated postoperative courses, with one case ending in the death of the patient. Two patients required tracheostomy. According to McCormick's classification, 7 (23 %) of the 31 operations resulted in aggravation and 23 (74 %) in no change. Considering the seven patients with aggravation at discharge, four patients (60 %) returned to their preoperative status, one (14 %) improved but remained below his preoperative McCormick grade and two (29 %) did not improve. At last follow-up, KPS was ameliorated in 53 %, stable in 40 % and worsened in 7 % of cases. CONCLUSION: Surgery of medulla oblongata hemangioblastomas is a challenging procedure characterized by an acceptable morbidity. Transient morbidity is not negligible even if the long-term outcome is in most cases favorable. A compromised neurological condition seems to be the best predictor of unfavorable outcome.

Germinoma of the medulla oblongata - A case report.

We describe a case of primary intracranial medulla oblongata germinoma in a 23-year-old female who presented with deteriorating balance and mobility. Imaging demonstrated an exophytic lesion arising from the dorsal medulla oblongata and extending into the fourth ventricle. The tissue sample was obtained via suboccipital craniotomy and a diagnosis of a primary medullary germinoma was made. The patient underwent whole craniospinal axis radiotherapy and remains well and recurrence-free at 1-year follow up.

Granular cell tumors in the central nervous system: a report on eight cases and a literature review.

OBJECTIVE: Granular cell tumors (GCTs) in the central nervous system (CNS) are extremely rare. We report here a series of eight GCTs at various locations in the CNS and provide a full review of the published literature. METHODS: Eight patients with pathologically confirmed GCT in the CNS were retrospectively reviewed. The patients were followed up via telephone interview or an outpatient department. RESULTS: Five patients were female, and three were male. Of the eight tumors, three were located at the sellar region, two were located in the spinal canal, one was located at the cerebral hemisphere, one was parasellar-nasal communicating, and one was combined with an enterogenous cyst at the ventral aspect of the medulla oblongata. Six patients were symptomatic, and two patients were found incidentally. Most GCTs tended to be homogeneous and well defined on radiological images. The parasellar-nasal communicating GCT showed destruction of the skull base and an evident cystic component in the sphenoid sinus. The various GCTs had similar histological features, and they tended to be histologically benign. Most tumors did not recur after the operation. After subtotal resection, one residual spinal GCT regrew during the follow-up period. The patient with the parasellar-nasal communicating GCT developed progressive visual loss in the right eye after the operation; and she received adjuvant radiation therapy. CONCLUSION: GCTs at different locations in the CNS can have significantly different clinical features and should be considered distinct entities. Except for the granular cell astrocytoma (GCA), most GCTs in the CNS tended to be benign. Malignant GCTs are rare and difficult to treat.

[A Case of an Abdominal Desmoplastic Small Round Cell Tumor with Metastasis in the Medulla Oblongata].

A desmoplastic small round cell tumor(DSRCT)is a very rare malignant tumor that mainly occurs in the intra-abdominal cavity in young adults.This neoplasm has an extremely poor prognosis, with a clinical course characterized by rapid progression and metastasis.We present a 31-year-old man who presented with chief complaints of dysphagia, ataxic gait, and hoarseness.He first underwent surgical resection of a tumor in the medulla oblongata; however, the lesion was suspected to be a metastatic neoplasm.Following a thorough medical examination, the patient was diagnosed with retroperitoneal DSRCT with multiple metastatic lesions.He received multidisciplinary treatment including debulking surgery for the primary lesion; radiotherapy for metastatic lesions in the brain, abdomen, and cervical lymph nodes; hepatic artery embolization for liver metastasis; and systemic chemotherapy.The patient died of progressive disease 17 months after the initial diagnosis.

Surgical injury in the neonatal rat alters the adult pattern of descending modulation from the rostroventral medulla.

BACKGROUND: Neonatal pain and injury can alter long-term sensory thresholds. Descending rostroventral medulla (RVM) pathways can inhibit or facilitate spinal nociceptive processing in adulthood. As these pathways undergo significant postnatal maturation, the authors evaluated long-term effects of neonatal surgical injury on RVM descending modulation. METHODS: Plantar hind paw or forepaw incisions were performed in anesthetized postnatal day (P)3 Sprague-Dawley rats. Controls received anesthesia only. Hind limb mechanical and thermal withdrawal thresholds were measured to 6 weeks of age (adult). Additional groups received pre- and post-incision sciatic nerve levobupivacaine or saline. Hind paw nociceptive reflex sensitivity was quantified in anesthetized adult rats using biceps femoris electromyography, and the effect of RVM electrical stimulation (5-200 µA) measured as percentage change from baseline. RESULTS: In adult rats with previous neonatal incision (n = 9), all intensities of RVM stimulation decreased hind limb reflex sensitivity, in contrast to the typical bimodal pattern of facilitation and inhibition with increasing RVM stimulus intensity in controls (n = 5) (uninjured vs. neonatally incised, P < 0.001). Neonatal incision of the contralateral hind paw or forepaw also resulted in RVM inhibition of hind paw nociceptive reflexes at all stimulation intensities. Behavioral mechanical threshold (mean ± SEM, 28.1 ± 8 vs. 21.3 ± 1.2 g, P < 0.001) and thermal latency (7.1 ± 0.4 vs. 5.3 ± 0.3 s, P < 0.05) were increased in both hind paws after unilateral neonatal incision. Neonatal perioperative sciatic nerve blockade prevented injury-induced alterations in RVM descending control. CONCLUSIONS: Neonatal surgical injury alters the postnatal development of RVM descending control, resulting in a predominance of descending inhibition and generalized reduction in baseline reflex sensitivity. Prevention by local anesthetic blockade highlights the importance of neonatal perioperative analgesia.

Telo-velar approach to fourth-ventricle tumours: how I do it.

BACKGROUND: The "telo-velar" approach is an alternative to cerebellar splitting to gain access to the fourth ventricle through the so-called cerebello-medullary fissure (CMF). METHOD: In this approach, the CMF is exposed and access to the ventricle is obtained by incising the tela chorioidea and inferior medullary velum. This approach enables the exploration of the entire ventricle cavity from the obex to the aqueduct. CONCLUSIONS: The exposure of the fourth ventricle is satisfactory and the floor of the fourth ventricle can be visualised early and protected. The extent of resection and outcome are satisfactory in most patients, including those with large tumours or lesions attached to the lateral or superolateral recesses of the ventricle. The deep rostral tumour attachment is the main limitation of the telo-velar approach. KEY POINTS: • Early exposure of the interface lesion-floor of the fourth ventricle favours a safer tumour dissection. • We feel that resection of tonsils is not necessary in the surgical setting. • The posterior arch of C1 should be removed only if the tonsils are below the level of the foramen magnum. • The improved access to the lateral recess of the ventricle makes the telo-velar approach particularly effective in lesions attached to cerebellar peduncles. • The wide dissection of the cerebello-medullary fissure and gentle tonsils retraction may prevent from the occurrence of cerebellar mutism or other major cerebellar dysfunctions. • Even the bilateral opening of the CMF does not result in cerebellar mutism if wide and cautious dissection, avoiding retraction and vascular injuries, is obtained. • The exposure of the fourth ventricle was satisfactory also in patients harbouring lesions attached to the lateral or even the superolateral recesses of the ventricle. • A deep rostral tumour attachment seems to be, at least in our experience, the main specific limitation of the telo-velar approach. • The risk of hydrocephalus can be reduced by opening of the fissure bilaterally, exposing the aqueduct, and by cisterna magna-fourth ventricle communication augmentation. • The EVD is taken in place for 48-72 h to prevent possible abrupt increase of the intracranial pressure and to favour wound closure.

[Brainstem cavernous malformation and its surgical treatment].

OBJECTIVE: To analyze the clinical characteristics and surgery approach for patients with brainstem cavernous malformation (BSCM). METHODS: The clinical data of 23 BSCM patients (5 cases at midbrain, 16 cases at pons, and 2 cases at medulla) treated in the Second Affiliated Hospital Zhejiang University School of Medicine from July 2003 to June 2014 were retrospectively reviewed. The medical history, radiological findings, operation records, postoperative course and follow-up results were analyzed. RESULTS: Suboccipital approach, retrosigmoid approach, subtentorial supracerebella approach, Poppen approach, pterional approach, Kawase approach, interhemispheric transcallosal third ventrical approach were applied for the surgery of BSCM patients. Among them, Kawase approach and interhemispheric transcallosal third ventrical approach were firstly reported in treatment of BSCM. Total resection was achieved in 22 cases. Neurological function was improved in 15 cases, unchanged in 7 cases and deteriorated in 1 case. Fifteen cases were followed up for a mean period of 3.5 years and signs of recurrence was found. CONCLUSION: Proper selection of surgical approach is important to assure total resection of the lesions, to protect surrounding normal vital structures and to avoid post-surgical complications.