Athanasios K. Petridis

Spinal cord compression caused by idiopathic intradural arachnoid cysts of the spine: review of the literature and illustrated case

Intradural spinal arachnoid cysts with cord compression are rare. When becoming symptomatic they cause variable symptoms involving gait disturbance, paraparesis or tetraparesis and neuropathic pain, decreasing significantly the patients’ life quality. The extension of such cysts averages 3.7 vertebral bodies. The diagnosis is clinical and radiological with the use of MRI, CT myelography or a combination of both. The best treatment option is complete removal of the cyst. However, even when paresis is regressing there is no good recovery from neuropathic pain. Laminectomy approach can cause postoperative complications especially when the cyst(s) expand(s) in more than one level. Alternatively, a cyst fenestration can be performed, including the levels of the maximal spinal cord compression. The clinical outcome is as good as after the cyst resection enabling the patient to walk again. The neuropathic pain may persist and require medication. A clinical case is presented, and the literature is reviewed. In the present case we report a patient with intradural arachnoid cysts extending from T6 to L2 and causing severe gait ataxia as well as neuropathic pain and hypaesthesia. The spinal-cord was compressed at T8 and T12. Surgical treatment with partial cyst resection in the compressed levels with an interlaminar approach brought similar results as complete resection. The patient was able to walk without help which was not possible before surgery. The cysts’ extension is impressive as well as the minimal operative procedure.

Vertebral artery decompression in a patient with rotational occlusion

SummaryWe report a patient who suffered drop attacks during head reclination. Computer tomography of the cervical spine demonstrated a stenotic right vertebral artery at C4/5. However, Doppler ultrasonography of the vertebral artery showed no abnormality. Angiography confirmed complete occlusion of the left vertebral and a stenosis of the right vertebral artery. Dynamic angiography indicated occlusion of the stenotic region on the right side during reclination of the head. Surgery using a posterior approach with decompression of the vertebral artery, lead to an excellent outcome and the patient left the hospital without any symptoms. Therefore, in patients with drop attacks and normal ultrasonography, a stenosis of the vertebral artery caused by a spondylophytic compression could still be the cause. At worst, the stenosis could lead to brain infarction if left untreated. Dynamic angiography is crucial for the diagnosis and surgical decompression has excellent results.

Brain-derived neurotrophic factor levels influence the balance of migration and differentiation of subventricular zone cells, but not guidance to the olfactory bulb

New progenitor cells in the subventricular zone (SVZ) migrate rostrally and differentiate into interneurons in the olfactory bulb (OB) throughout life. Brain-derived neurotrophic factor (BDNF) may influence the normal progression of this migration. In the present study, mouse SVZ explant cultures were used to investigate how BDNF modulates the behavior of these migrating progenitors. Concentrations of BDNF in the physiological range (e.g. 1ng/mL) stimulated migration, whereas doses of 10 ng/mL or higher induced SVZ cell differentiation and reduced migration. Pharmacological inhibition of the mitogen-activated protein kinase (MAPK) pathway blocked the BDNF-induced differentiation of SVZ progenitors, indicating that differentiation of SVZ progenitors in response to high-dose BDNF is initiated through MAPK. Physiological concentrations of BDNF, like the presence of polysialic acid in the tissue, stimulated migration of cells from the explant without affecting the speed at which this occurs. Interestingly, in vivo immunohistochemical and molecular analysis showed similar levels of BDNF in both the SVZ and OB; that is, there was no positive gradient attracting SVZ cells towards the OB. Our data show that SVZ cells respond differently to different concentrations of BDNF.

Polysialic acid overexpression in malignant astrocytomas

ObjectivePolysialic acid (PSA) is a carbohydrate binding on the neural cell adhesion molecule NCAM and impedes cell-cell interactions. It prevents neural progenitor cell differentiation and promotes their migration. Highly malignant tumours like small cell lung carcinoma (SCLC) also overexpress PSA and this correlates with a negative prognosis.MethodsIntra-operatively collected biopsies from 30 patients with different astrocytoma grades were immuno-histochemically examined to identify expression of PSA.ResultsAstrocytoma grade I and II had 4% PSA expressing cells whereas in grade III and IV the number of PSA expressing cells was 45%. This difference was statistically highly significant.ConclusionIn this short communication we show that highly malignant astrocytomas express significantly more PSA compared to less malignant astrocytomas. Cleavage of PSA could be used in future therapeutic approaches.

The value of intraoperative sonography in low grade glioma surgery

OBJECTIVE There is a number of different methods to localize a glioma intraoperatively. Neuronavigation, intraoperative MRI, 5-aminolevulinic acid, as well as intraoperative sonography. Every method has its advantages and disadvantages. Low grade gliomas do not show a specific signal with 5-aminolevulinic acid and are difficult to distinguish macroscopically from normal tissue. In the present study we stress out the importance of intraoperative diagnostic ultrasound for localization of low grade gliomas. METHODS We retrospectively evaluated the charts and MRIs of 34 patients with low grade gliomas operated in our department from 2011 until December 2014. The efficacy of ultrasound as an intraoperative navigational tool was assessed. In 15 patients ultrasound was used and in 19 not. Only histologically proven low grades gliomas (astrocytomas grade II) were evaluated. RESULTS In none of the patients where ultrasound (combined with neuronavigation) was used (N=15) to find the tumors, the target was missed, whereas the exclusive use of neuronavigation missed the target in 5 of 19 cases of small subcortical low grade gliomas. CONCLUSIONS Intraoperative ultrasound is an excellent tool in localizing low grade gliomas intraoperatively. It is an inexpensive, real time neuronavigational tool, which overcomes brain shift. Even when identifying the tumors with ultrasound is very reliable, the extend of resection and the decision to remove any residual tumor with the help of ultrasound is at the moment unreliable.

The Role of the Pterional Approach in the Surgical Treatment of Olfactory Groove Meningiomas: A 20-year Experience

Background Olfactory groove meningiomas remain surgically challenging. The common microsurgical approaches suffer from late exposure of the neurovascular structures. Conversely, the pterional approach has the advantage of early dissection of the posterior neurovascular complex. Methods We reviewed the records of patients treated for olfactory groove meningioma in our department between 1991 and 2010. A total of 61 patients underwent removal of olfactory groove meningiomas via the pterional approach. These included 58 primary and 3 recurrent tumors. Mean overall follow-up time was 122 months. Results Early exposure and dissection of the internal carotid artery, middle cerebral artery, anterior cerebral artery, and optic nerve was feasible in all cases. Complete tumor removal was achieved in 60 patients. Morbidity and mortality rates were 26% and 1.6% respectively. Postoperative complications included epileptic seizures (five patients) and cerebrospinal fluid (CSF) leak (two patients). During follow-up, we recorded three tumor recurrences. Conclusions The pterional approach appears to be an excellent solution for the treatment of olfactory groove meningiomas. Its foremost advantage is early visualization of the posterior neurovascular complex. Moreover, it allows frontal sinus preservation and timely tumor devascularization and avoids excessive brain retraction. The pterional view is familiar to most neurosurgeons and therefore the transition to this technique is fairly straightforward.

The transmaxillary endoscopic approach to the orbit

ObjectiveIn this surgical-anatomical cadaveric study we investigate the feasibility of the transmaxillary endoscopic approach to the intraorbital space. Anatomical landmarks are defined, the endoscopic view in the orbital space is studied and complications that can occur are discussed.MethodsNine formalin-fixed heads were used to study the transmaxillary endoscopic approach to the orbit. The approach was used twice on each head (once for each maxilla). Therefore, we report our results on 18 transmaxillary intraorbital approaches. For better differentiation of anatomical structures, the veins and arteries were injected with blue and red plastic respectively in six cadaveric heads.ResultsThe transmaxillary approach enables viewing the inferior intraconal structures without endangering the infraorbital nerve and its artery and without diversion of the inferior rectus muscle. The optic nerve was visualised more easily through the approach medial to the inferior rectus muscle instead of lateral to the muscle since the ciliary nerves are in the way in the lateral approach. The combination of the approaches medial and lateral to the inferior rectus muscle allows very good identification of all important anatomical structures in the inferior intraconal space.ConclusionThe transmaxillary endoscopic approach to the orbit is a useful new approach in the surgical armamentarium for orbital lesions. The overview of the inferior part of the orbit is excellent, and the lateral part of the optic nerve can be visualised. Careful anatomical dissection allows visualisation of important anatomical structures in the orbit without damaging nerves or arteries.

A case of aplasia of the posterior arch of the atlas mimicking fracture: Review of the literature

Congenital absence of the posterior atlas arch is rare (Osti et al., 2006). Most congenital anomalies of the atlantal arch are found incidentally in asymptomatic patients (Senoglu et al., 2007). Its detection, however, in the onset of acute cervical spine injury is of great importance as it can be often mistaken as a Jefferson’s fracture (Gangopadhyay and Aslam, 2003). All precautions should be taken to avoid an injury of the spinal cord until proven that no traumatic injury has taken place. The clinical manifestations vary from totally asymptomatic patients who sustained mild traumas to others who appear with signs of myelopathy (Torreman et al.,1996; Phan et al., 1998; Urasaki et al., 2001; Klimo et al., 2003). Plain radiographs which show the presence of atlas pathology should be followed with CT scans and MRI in the presence of neurological symptoms. When instability of the upper cervical spine via flexion and extension movements is demonstrated, a dorsal stabilisation or atlas fragment resection should be performed (Klimo et al., 2003). A 25-year-old female patient with a mild head trauma as a result of a syncopal episode and fall is reported in this case. Up on admission she complained only of mild tenderness in the cervical spine and mild headaches without dizziness or vomiting. Her neurological status was normal. The cervical pain would not increase by head turning, flexion, or extension. No irradiating pain was indicated. Plain radiographs of the cervical spine (Fig. 1a and 1b) revealed an abnormality of the posterior arch of the atlas, and to rule out a fracture a CT scan was obtained (Figure 1c). The diagnosis of a congenital failure (atlas aplasia) without the presence of fracture, intraspinal or paraspinal haematoma, or compression of the spinal cord was confirmed. Furthermore, no signs of luxation or rupture of the ligaments was shown. Because the patient did not show any neurological symptoms and signs, an MRI scan was not performed. She received pain killers and muscle relaxants and was discharged free of symptoms the following day. Approximately, 10% of cervical spine fractures are fractures of the atlas (de Zoete and Langeveld, 2007). Congenital partial aplasia of the atlas on the other hand is even more rare and includes 4% for Type A defects and 0.69% for Type B through E defects, according to the Currarino classification (Currarino et al., 1994; Caro et al., 2008). Embryologically, there are three ossification centers of the atlas: an anterior and two lateral, which form the anterior tubercle and the lateral masses and posterior arch, respectively. By the 7th gestational week, the lateral centers have extended dorsally to form the posterior arch (Klimo et al., 2003). Defects of the posterior arch are thought to occur because of the failure of local chondrogenesis rather than subsequent ossification (von Torklus and Gehle, 1972). As Huggare suggested, there is also an intimate developmental association between the upper part of the cervical spine and the craniofacial complex (Huggare, 1995). The clinical presentation varies from mild neck pain without neurological deficits to myelopathy or Lhermitte sign due to cervical spinal stenosis, particularly, by extension or flexion of the cervical spine (Torreman et al., 1996; Phan et al., 1998; Sharma et al., 2000; Klimo et al., 2003; O’Sullivan et al., 2004, Sagiuchi et al., 2006). Therefore, it is of paramount importance to know this anatomical entity and accordingly consult the patients to avoid contact sports and other strenuous athletic endeavors (Castaño-Duque et al., 1997). The clinical evaluation can reveal motor or sensory deficits, hyperreflexia, or Babinski sign. Diagnostic evaluation includes plain radiographs of the cervical spine and CT scans, which should rule out the presence of a fracture (Fig. 1). In patients with clinical signs of myelopathy, Lhermitte sign, sensory or motor disorders, an MRI scan should be performed. If the symptoms worsen by flexion or exten-

An introduction to the pathophysiology of aneurysmal subarachnoid hemorrhage

Pathophysiological processes following subarachnoid hemorrhage (SAH) present survivors of the initial bleeding with a high risk of morbidity and mortality during the course of the disease. As angiographic vasospasm is strongly associated with delayed cerebral ischemia (DCI) and clinical outcome, clinical trials in the last few decades focused on prevention of these angiographic spasms. Despite all efforts, no new pharmacological agents have shown to improve patient outcome. As such, it has become clear that our understanding of the pathophysiology of SAH is incomplete and we need to reevaluate our concepts on the complex pathophysiological process following SAH. Angiographic vasospasm is probably important. However, a unifying theory for the pathophysiological changes following SAH has yet not been described. Some of these changes may be causally connected or present themselves as an epiphenomenon of an associated process. A causal connection between DCI and early brain injury (EBI) would mean that future therapies should address EBI more specifically. If the mechanisms following SAH display no causal pathophysiological connection but are rather evoked by the subarachnoid blood and its degradation production, multiple treatment strategies addressing the different pathophysiological mechanisms are required. The discrepancy between experimental and clinical SAH could be one reason for unsuccessful translational results.

Efficacy of a new video-based training model in spinal surgery.

Background: An important part of neurosurgical training is the improvement of surgical skills. Acquiring microsurgical skills follows a learning curve, influenced by specific exercises, feedback, and training. Aim of training should be rapid learning success. The study shows the way in which video-based training can influence the learning curve. Methods: Over a period of 18 months (2011-2012) 12 residents were evaluated in spinal surgery (12 cases per resident) by a skilled evaluator based on different criteria. The evaluation criteria (exposition of important anatomy, intraoperative bleeding, efficacy of using bipolar cauterization) were weighted and added to a single quality-score. The participating residents were divided into two groups. Only one group (n = 5) received video-based training. Results: Residents showed an individually different but explicit increase in microsurgical skills. The quality-score during the first surgery compared with the end point of the study demonstrated a faster improvement of surgical skills in the group with video-based training than in the group without special training. Considering all residents together, the video-training group displayed a steeper gradient of microsurgical success. Comparison of the single residents microsurgical skills showed individual disparities. Various biases that influence the learning success are under examination. Conclusion: Video-based training can improve microsurgical skills, leading to an improved learning curve. An earlier entry of the learning curve plateau in the video-training group promotes a higher acquisition of surgical skills. Because of the positive effect, we plan to apply the video-based training model to other neurosurgical subspecialties, especially neurovascular and skull base surgery.