Jan Frederick Cornelius

Anatomical variations of the V2 segment of the vertebral artery.

OBJECTIVE: Our goal was to evaluate the incidence of anatomic variations of the V2 segment (from its entrance into the transverse canal to C2) of the vertebral artery. Ignoring such variations during anterior or lateral approach to the cervical spine can lead to inadvertent injury and potentially serious complications. METHODS: We studied the course of 500 vertebral arteries on 200 magnetic resonance imaging and 50 contrast-enhanced computed tomographic scans. RESULTS: The vertebral artery entered the C6 transverse foramen in 93.0% of all specimens. An abnormal level of entrance was observed in 7.0% of specimens (35 courses), with a level of entrance into the C3, C4, C5, or C7 transverse foramen, respectively, in 0.2% (n = 1; 2.9% of all anomalies), 1.0% (n = 5; 14.3% of all anomalies), 5.0% (n = 25; 71.4% of all anomalies), and 0.8% (n = 4; 11.4% of all anomalies) of all specimens. Seventeen (48.6%) abnormalities were right-sided and 18 (51.4%) were left-sided. Thirty-one out of 250 patients (12.4%) had a unilateral anomaly and two had a bilateral anomaly (0.8%). In cases of abnormal entrance into the transverse foramen on computed tomographic images (n = 6), the area of the unfilled transverse foramens was significantly smaller than the contralateral filled foramen (P < 0.0001) and was significantly smaller than the filled foramen of all patients at the same level (P < 0.0001). In five patients (2.0%), the vertebral artery formed a medial loop either into an unusually large transverse foramen whose internal border was medial to the uncovertebral joint or into the intervertebral foramen. CONCLUSION: The incidence of anatomic variations of the vertebral artery V2 segment is high. Potentially dangerous conditions can be detected on preoperative imaging.

Antero-lateral approach to the V3 segment of the vertebral artery.

OBJECTIVE: We describe our surgical technique of exposure, control, and transposition of the third segment of the vertebral artery (VA V3 segment). METHODS: The VA V3 segment extends from the C2 transverse foramen to the dura mater of the foramen magnum. It initially courses vertically between the C2 and C1 transverse foramens, then runs horizontally over the atlas groove, and finally obliquely upwards before piercing the dura mater. Exposure of the VA V3 segment through an antero-lateral approach is performed by passing medially to the sternomastoid muscle. After exposure and protection of the spinal accessory nerve, the C1 transverse process is identified below and in front of the mastoid tip. The small muscles that insert on it are cut to expose the C1-C2 portion. The inferior aspect of the horizontal portion is safely separated from the atlas groove by elevating the subperiosteal plane and the superior aspect is freed by a cut a few millimeters above the VA on the occipital condyle. Complete unroofing of the C1 transverse foramen is achieved by resecting the bone while leaving intact the subperiosteal plane. The VA then can be transposed. Venous bleedings during the dissection from periosteal sheath tearing can be controlled by direct bipolar coagulation. RESULTS: The control of the VA V3 segment is essentially used for lesions in the VA vicinity and to improve the surgical exposure at the craniocervical junction level. Indications therefore are tumoral removal, VA decompression, and rarely, nowadays, VA revascularization. CONCLUSION: Perfect knowledge of the anatomy and the surgical technique permits a safe exposure, control, and transposition of the VA V3 segment. This is the first step of many surgical procedures.

The trigemino-cardiac reflex in adults: own experience

The trigemino-cardiac reflex The trigemino-cardiac reflex (TCR) has previously been described in the literature as a reflexive response composed of bradycardia, hypotension and gastric hypermotility seen upon mechanical stimulation anywhere in the distribution of the trigeminal nerve [1–5]. Based on the initial rabbit neurostimulation experiments of Kumada et al. in 1977 [6], TCR was first observed by Schaller et al. in 1999 during neurosurgical operations [5]. By systematic observation, the incidence of the TCR during neurosurgical procedures around the trigeminal nerve was shown to be approximately 10–18%, independently of the surgeon who operated or the approach that was used [3,7–12]. In their key works, Schaller et al. first defined TCR in detail, and their observations are at present generally accepted [3,5,13–15].

Anterolateral approach to the V2 segment of the vertebral artery.

OBJECTIVE We describe our surgical technique of exposure and control of the second segment of the vertebral artery (VA V2 segment). Our basic principle is that working in the VA vicinity is more confident under visual control. METHODS The VA V2 segment extends classically in and between the transverse processes from C6 to C2. This segment can be exposed through an anterolateral approach, passing medially to the sternocleidomastoid muscle and laterally to the internal jugular vein. Except in case of anatomic variation, the VA V2 segment is protected by the transverse processes bone, even if a pathological process displaces the VA along its course between them. The safest technique to expose the VA V2 segment then is to reach first the transverse process by cutting the longus colli muscle. Afterward, dividing intertransversary muscles permits exposure of and safely controls the VA by following its course. If required, the VA V2 segment can even be freed by opening the transverse process as far as the dissection is performed in the subperiosteal plane. In fact, the VA V2 segment is surrounded by a venous plexus and a periosteal sheath. This sheath gives a plane out of which the dissection is safe, avoiding troublesome venous bleeding or VA damage. RESULTS This technique is very efficient for degenerative disorders, hour glass tumors, and vascular surgeries. CONCLUSION Exposure and control of the VA V2 segment is safe if anatomy and variations are perfectly known, and if a rigorous step-by-step surgical technique is followed.

Multilevel oblique corpectomies: surgical indications and technique.

OBJECTIVE We describe extensively the multilevel oblique corpectomy technique with its advantages, disadvantages, indications, and biomechanical effects. This procedure is an alternative to the anterior corpectomy. METHODS Multilevel oblique corpectomy can be indicated in spondylotic myelopathy, whether or not it is associated with unilateral radiculopathy. Certain conditions must be fulfilled: anterior compression must be predominant, the spine must be kyphotic or straight, preoperative instability has to be excluded, and intervertebral discs have to be dehydrated and collapsed. resultS The lateral aspect of the cervical spine is reached and the vertebral artery is controlled through a lateral approach. The lateral part of the pathological intervertebral discs is removed. Then, the lateral portion of the vertebral body is drilled to create an 8-mm wide vertical trench. When the posterior cortical bone as well as the superior and inferior end plates are reached, the microscope is moved obliquely to extend the drilling horizontally as long as required, up to the contralateral pedicle if necessary. Next, the posterior cortical bone and the posterior longitudinal ligament are removed to completely decompress the spinal cord. In the case of radiculopathy, the ipsilateral foramen can be completely opened by taking away the uncovertebral joint after its lateral aspect has been separated from the vertebral artery. CONCLUSION The multilevel oblique corpectomy technique allows wide anterior decompression of the spinal cord and complete unilateral nerve root decompression. Using this technique, the spinal stability is preserved and osteoarthrodesis is not required. Spinal motions are preserved and appear close to normal.

Microsurgical cervical nerve root decompression by anterolateral approach.

OBJECTIVE: Cervical radiculopathy caused by a posterolateral soft disc herniation or spondylosis is a common pathology. METHODS: Decompression of a stressed cervical nerve root is a routine neurosurgical procedure. Most of the time it is achieved through an anterior approach and, less frequently, through a posterior approach in specific indications. RESULTS: According to the principles that an anterolateral compression must directly be reached and that working in the vicinity of the vertebral artery is safe under visual control, we developed the anterolateral approach to the cervical intervertebral foramen and the nerve root using a minimally invasive technique to remove the offending process. CONCLUSION: Microsurgical cervical nerve root decompression by anterolateral approach is a minimally invasive technique, permitting one to remove the offending process staightforwardly. The disc and bone resections are minimal. This method avoids osteoarthrodesis or arthroplasty with disc prosthesis. This technique is efficient with good results and low morbidity.

Oxygen-conserving implications of the trigemino-cardiac reflex in the brain: the molecular basis of neuroprotection?

defined as a sudden dysrhythmia with arterial hypotension accompanied by apnea or gastric hypermotility after stimulation of any of the sensory branches of the trigeminal nerve (1). The sensory nerve endings of the trigeminal nerve transmit neuronal signals via the Gasserian ganglion to the sensory nucleus of the trigeminal nerve (2). This initiates adjustments in the systemic and cerebral circulation to adjust the cerebral blood flow in a manner that is not yet well understood (3). Extensive investigations in animals have documented the involvement of supramedullary regions of the brain in cardiovascular regulation (4–6). It appears that the cerebrovascular response as part of the TCR is generated by the activation of the reticulospinal neurons of the rostral ventrolateral medulla (RVLM) to elevate cerebral blood flow (CBF) reflexively and most likely slow cerebral metabolism as part of an oxygen-conserving reflex. The existence of such endogenous neuroprotective strategies also may have an important physiological role namely by stabilizing the brain function and by the prevention of permanent cerebral ischemic damage. However, examinations of

Erratum to: Effect of augmentation techniques on the failure of pedicle screws under cranio-caudal cyclic loading

Purpose Augmentation of pedicle screws is recommended in selected indications (for instance: osteoporosis). Generally, there are two techniques for pedicle screw augmentation: inserting the screw in the non cured cement and in situ-augmentation with cannulated fenestrated screws, which can be applied percutaneously. Most of the published studies used an axial pull out test for evaluation of the pedicle screw anchorage. However, the loading and the failure mode of pullout tests do not simulate the cranio-caudal in vivo loading and failure mechanism of pedicle screws. The purpose of the present study was to assess the fixation effects of different augmentation techniques (including percutaneous cement application) and to investigate pedicle screw loosening under physiological cyclic cranio-caudal loading.

5-Aminolevulinic Acid and 18F-FET-PET as Metabolic Imaging Tools for Surgery of a Recurrent Skull Base Meningioma

Background Metabolic imaging technologies such as 5-aminolevulinic acid (ALA) fluorescence-guided resection and positron-emission tomography (PET) imaging have improved glioma surgery within the last decade. At present, these tools are not routinely used in meningioma surgery. Objective We present a case of a complex-shaped, recurrent skull base meningioma where 5-ALA fluorescence-guidance and (18)F-fluoroethyltyrosine (FET)-PET-imaging facilitated surgical resection. Material and Methods The patient underwent surgery via a combined transcranial/transnasal endoscopic approach. What was original is that both the microscope and the endoscope were equipped for 5-ALA fluorescence-guided surgery, respectively. Furthermore, preoperative FET-PET imaging was fused with computed tomography (CT) and magnetic resonance imaging (MRI) data for intraoperative navigation. The case richly illustrated the performance of the different modalities. Conclusions Metabolic imaging tools such as 5-ALA fluorescence-guided resection and navigated FET-PET were helpful for the resection of this complex-shaped, recurrent skull base meningioma. 5-ALA fluorescence was useful to dissect the adherent interface between tumor and brain. Furthermore, it helped to delineate tumor margins in the nasal cavity. FET-PET improved the assessment of bony and dural infiltration. We hypothesize that these imaging technologies may reduce recurrence rates through better visualization of tumor tissue that might be left unintentionally. This has to be verified in larger, prospective trials.

Osteoid osteomas and osteoblastomas of the occipitocervical junction.

Study Design. We describe our surgical experience to remove osteoid osteomas and osteoblastomas of the occipitocervical junction. In this location, vertebral artery vicinity requires special consideration. Objectives. We illustrate our surgical approaches to remove lesions confidently, while minimizing bone resection to preserve stability. Summary of Background Data. Up until now, osteoid osteomas and osteoblastomas of the occipitocervical junction are reported as case reports. Several treatment methods have been described to treat osteoid osteomas. Nevertheless, surgery is the treatment of choice for lesions located in the C0–C2 region. Methods. A retrospective review of 7 patients, including 5 men and 2 women, with a mean age of 21.0 years (range 3.0–38.0) was conducted. Clinical outcomes were evaluated immediately and after a mean follow-up of 27.6 months. Results. There were 6 and 1 patients who underwent surgery with the anterolateral and posterolateral approaches, respectively. In osteoid osteomas, the nidus was removed, and the peripheral condensation was drilled up to normal bone (n = 4) or partially resected (n = 2). One osteoblastoma was removed extensively up to soft tissues. No osteo-arthrodesis was performed. Before surgery, all patients complained of pain, 3 presented with neck stiffness, and 2 with a torticollis. Immediately after surgery, all complaints disappeared. One patient underwent repeat surgery 15 months later for a recurrence. At the end of the follow-up, all patients were symptom-free, and partially resected peripheral condensations were stable on computerized tomography. Conclusions. Removal of osteoid osteomas and osteoblastomas of the occipitocervical junction is safe and efficient. Stability is preserved if more than half the joints are preserved with a proper surgical approach that minimizes bone resection.