Schwannoma in Hemophilic Patient: Surgical Considerations

Introduction: Schwannoma is a benign, encapsulated, tumor that arises from Schwann cells of myelinated nerves. In this report, we present a case of schwannoma in a hemophilic patient and its surgical considerations related to bleeding complications. Case Presentation: We present a case of a 27-year-old male coming to our center with a chief complaint of a painless, non-progressive growing mass on the back of his head since a year prior to admission. Physical examination showed that the mass was mobile, firm, and had a welldefined margin beneath the scalp. His radiograph showed a soft tissue mass beneath the scalp. MRI demonstrated a dense-multilobulated mass without intracranial infiltration. The patient had hemophilia A from the age of 5. We performed marginal excision of the mass with regiments of factor VIII (FVIII) concentrates preoperatively, intraoperatively, and postoperatively. Pathology was consistent with schwannoma.Conclusions: Schwannoma management in hemophilic patients needs several considerations. Perioperative planning plays a major part in the management of patients with tumors and hemophilia to prevent bleeding complications.

Nasal Schwannoma

Introduction A schwannoma is a benign nerve sheath tumuor of myelinated nerves arising from Schwann cells. In the head and neck region, the most common site is the eighth cranial nerve (vestibulocochlear). Only 4% of schwannomas seen in the head and neck region arise from the nose and paranasal sinuses involving branches of the trigeminal nerve (ophthalmic or maxillary) or from the autonomic nervous system. Case Report A 29 year old female patient presented to the Ear, Nose and Throat Out Patient Department with the complaints of left sided nasal obstruction and left sided nasal bleed. On anterior rhinoscopy, a single, smooth, greyish, non-pulsatile polypoidal mass was seen in the left nasal cavity seeming to be arising medial to middle turbinate. A provisional diagnosis of benign nasal mass was made and the patient underwent excision under general anaesthesia. On histopathology, an impression of Schwannoma was made. Discussion Sino-nasal schwannomas are a very rare entity with non specific imaging studies. A confirmatory diagnosis can be made only after histopathology. The treatment modality of choice is surgical excision of the mass, taking care to leave no residual, so as to prevent a recurrence.

Epstein-Barr Virus and Multiple Sclerosis

Multiple sclerosis (MS) is a neurologic disease affecting myelinated nerves in the central nervous system (CNS). The disease often debuts as a clinically isolated syndrome, e.g., optic neuritis (ON), which later develops into relapsing-remitting (RR) MS, with temporal attacks or primary progressive (PP) MS. Characteristic features of MS are inflammatory foci in the CNS and intrathecal synthesis of immunoglobulins (Igs), measured as an IgG index, oligoclonal bands (OCBs), or specific antibody indexes. Major predisposing factors for MS are certain tissue types (e.g., HLA DRB1*15:01), vitamin D deficiency, smoking, obesity, and infection with Epstein-Barr virus (EBV). Many of the clinical signs of MS described above can be explained by chronic/recurrent EBV infection and current models of EBV involvement suggest that RRMS may be caused by repeated entry of EBV-transformed B cells to the CNS in connection with attacks, while PPMS may be caused by more chronic activity of EBV-transformed B cells in the CNS. In line with the model of EBV’s role in MS, new treatments based on monoclonal antibodies (MAbs) targeting B cells have shown good efficacy in clinical trials both for RRMS and PPMS, while MAbs inhibiting B cell mobilization and entry to the CNS have shown efficacy in RRMS. Thus, these agents, which are now first line therapy in many patients, may be hypothesized to function by counteracting a chronic EBV infection.

A new mechanism controlling conduction in stretched myelinated nerves and a comprehensive nerve conduction model

Analysing published experimental findings this paper revealed that for myelinated nerves the conduction velocity (CV) increases on stretching out of the nerve, which has not been pointed out by anyone before. This apparently contradicts existing concepts since stretching out of a nerve fibre reduces its diameter which is expected to reduce the CV. Besides, the change is reversible and immediate, which cannot be explained with existing knowledge either. In order to explain this anomaly, the present work invoked a new resistance to ion flow between the nerve axon and the extracellular fluid created by interdigitated fingerlike processes of myelin sheaths coming from two sides of a node of Ranvier, analyzing published electron microscopic images. When stretched out, the gaps between the processes increase, decreasing the resistance to ion flow and thereby hastening depolarization, increasing CV in turn. The gaps close immediately on the release of the stretching force because of the pull of the elastic endoneurium, thus retrieving the original CV. To represent this new mechanism, a new resistive element has been added to the existing electrical model of a myelinated nerve, which is being claimed to be the dominant component that determines the conduction delay. Stretching also affects other nerve parameters and this paper developed a mathematical formulation involving all these parameters to show satisfactorily that CV indeed increases with stretching, in which the contribution of the proposed resistance dominates. The paper also proposed an appropriate modification of the representative schematic model commonly used to depict propagation of action potential in a myelinated nerve fibre. The suggested new mechanism and the resistance model is a breakthrough in the explanation of neural conduction and opens up the door for new study as well as for reviewing all previous experiments on myelinated nerves afresh. Bangladesh Journal of Medical Physics Vol.11 No.1 2018 P 38-56

The Science and Art of Nerve Fiber Teasing for Myelinated Nerves: Methodology and Interpretation

Nerve fiber teasing is a sensitive technique utilized in diagnostic neuropathology practice, laboratory research, and animal toxicity studies for characterizing changes in single myelinated nerve fibers over extended distances. In animal toxicity studies, a nerve portion (approximately 10 mm in length) is stained with Sudan black for 24 to 48 hours and then transferred into a drop of viscous medium (eg, glycerin) mounted on an adhesive-coated glass slide, positioning it such that the proximodistal orientation is known. Individual fibers are removed using fine forceps while the sample is viewed under a stereomicroscope. In general, lesions can be identified during teasing, but more detailed characterization and photodocumentation is undertaken once nerve fibers have been dried and coverslipped. Nerve fiber teasing is particularly useful for distinguishing early stages of axonal degeneration (which presents as ovoid fiber fragments in the midinternodal region) from segmental demyelination (which presents as loss of original myelin segments and their replacement by thinner, shorter segments in the absence of axonal damage). The slow, laborious nature of nerve fiber teasing dictates that the technique will be employed on a few samples as an auxiliary method to better define the pathogenesis of nerve lesions first identified by conventional histopathologic assessment.

Myelin can't change the basic mechanisms of axonal conduction

We propose a new hypothesis about the physical-chemical mechanisms of nerve conduction in myelinated nerves, tending to bridge the theoretical gap existing to date between the basic neuronal activity and its adaptation to myelination. All the considerations imply a simplification of the underlying theories, identifying a precise role for myelin. The ATP-supplying energetic role for myelin allows to overcome the theories that have not yet found a physical-chemical solid confirmation. A radical simplification of nerve conduction mechanism is envisaged: it can be supposed that this mechanism remains unaltered in the passage from the unmyelinated to the myelinated conditions.

Myelin can't change the basic mechanisms of axonal conduction

We propose a new hypothesis about the physical-chemical mechanisms of nerve conduction in myelinated nerves, tending to bridge the theoretical gap existing to date between the basic neuronal activity and its adaptation to myelination. All the considerations imply a simplification of the underlying theories, identifying a precise role for myelin. The ATP-supplying energetic role for myelin allows to overcome the theories that have not yet found a physical-chemical solid confirmation. A radical simplification of nerve conduction mechanism is envisaged: it can be supposed that this mechanism remains unaltered in the passage from the unmyelinated to the myelinated conditions.