Anatomic Alert: Spinal accessory nerve traversing a fenestrated internal jugular vein.

We present a case of the spinal accessory nerve traversing a fenestrated internal jugular vein. Awareness of this variant may be important in neurosurgical procedures that involve upper cervical exposures.

MR Neurographic Evaluation of Facial and Neck Pain: Normal and Abnormal Craniospinal Nerves below the Skull Base.

Cranial nerve disease outside the skull base is a common cause of facial and/or neck pain, which causes significant disability for patients and frustration for clinicians. Neuropathy in this region can be traumatic, idiopathic, or iatrogenic secondary to dental and surgical procedures. MR neurography is a modification of conventional MRI techniques dedicated to evaluation of peripheral nerves and is being increasingly used for imaging of peripheral neuropathies at various sites in the body. MR neurography facilitates assessment of different causes of craniofacial pain and cranial nerves and allows elegant depiction of a multitude of regional neuropathies. This article discusses the anatomy, pathologic conditions, and imaging findings of the commonly implicated but difficult to image infratentorial nerves, such as the peripheral trigeminal nerve and its branches, facial nerve, glossopharyngeal nerve, vagus nerve, hypoglossal nerve, and greater and lesser occipital nerves. ©RSNA, 2018.

Spinal nerve defects in mouse embryos prenatally exposed to valproic acid.

To examine in detail spinal nerve defects induced by prenatal exposure to valproic acid in mice, pregnant ICR mice were subcutaneously injected with a single dose of 400 mg/kg valproic acid on gestational day 6, 7, 8, or 9, and their embryos were observed on gestational day 10. The whole-mount immunostaining using an anti-neurofilament antibody allowed us to identify spinal nerve defects, such as a loss of bundle, anastomosis among bundles arising from adjacent segment, and a disrupted segmental pattern of the dorsal root ganglia, in valproic acid-exposed embryos. The prevalence of spinal nerve defects was the highest in the embryos exposed to valproic acid on gestational day 8 among the experimental groups. Then, effects of the administration dose of valproic acid on the prevalence of spinal nerve defects were examined on gestational day 10 and found to be dose-dependently increased. It was noteworthy that all embryos exposed to 600 mg/kg of valproic acid on gestational day 8 suffered spinal nerve defects. Folic acid (3 mg/kg/day) supplementation during gestational day 6-10 suppressed the prevalence of valproic acid-induced neural tube defects, which are common malformations in offspring prenatally exposed to valproic acid, but not that of spinal nerve defects. Thus, the spinal nerve defects due to prenatal valproic acid exposure might be induced by mechanisms different from those of neural tube defects. Because spinal nerve defects were predicted to be caused by the disrupted segmental arrangement of the somites and/or that of neural crest cells, which was the origin of the dorsal root ganglia and/or abnormal polarity of the somite, this mouse model with spinal nerve defects at high incidence would be useful to examine the effects of valproic acid on the somitogenesis and morphogenesis of somite-associated structures.

A unique case of intradural communicating branches between the accessory nerve and the dorsal roots of the cervical spinal nerves.

OBJECTIVE: The accessory nerve has cranial and spinal roots. The cranial roots emerge from the medulla, whereas the spinal roots arise from motor cells within the ventral horn of C1-C7 segments of the spinal cord. Communications have been described between the spinal accessory nerve rootlets and the dorsal rootlets of cervical spinal nerves. In the present case, we report a communication that has not been reported before and discuss the functional anatomy. MATERIALS AND METHODS: During the dissection of the craniovertebral junction of a 67-year-old formalin-fixed adult male cadaver, a connection between the spinal accessory nerve rootlets and the dorsal rootlets of the cervical spinal nerves was observed. RESULTS: A communication between the spinal rootlets of the accessory nerve and the dorsal roots of cervical spinal nerves was present on the right and left side. On the right, a communication between the accessory nerve spinal rootlet and the dorsal rootlet of the fourth cervical spinal nerve existed. On the left, there were two branches from the lowest accessory nerve spinal rootlet, one run ventrally and the other dorsally to the spinal rootlet and reached the dorsal root of third cervical spinal nerve. The dorsal root of C1 did not exist on either the right or the left side. Further, an unusual spinal accessory nerve formation was also observed. DISCUSSION: This case does not fit into any of the previously described classifications in the literature. Therefore, the different variations concerning the communications between the spinal rootlets of the accessory nerve and the cervical spinal nerves should be kept in mind during both surgical, especially radical neck dissections, and nonsurgical evaluations.

Islet1 selectively promotes peripheral axon outgrowth in Rohon-Beard primary sensory neurons.

We isolated a novel zebrafish mutant, lullaby (llb), and showed that the llb locus encodes the zebrafish orthologue of isl1. Rohon-Beard (RB) primary sensory neurons are multipolar neurons that extend their central axons longitudinally within the spinal cord and also extend their peripheral axons under the skin. In llb embryos, the outgrowth of the peripheral axons of RB neurons was selectively impaired, which correlated with down-regulation of the expression of dihydropyrimidinase-like 3 (dpysl3, also known as collapsin response mediator protein 4, crmp4). Antisense morpholino oligonucleotide (AMO)-mediated knockdown of dpysl3 inhibited the outgrowth of the peripheral axons of RB neurons, and semaphorin 3d (sema3d) AMO enhanced this effect. These data indicate that Dpysl3 is cooperating with Sema3d in the peripheral axon outgrowth, and Isl1 is required for the selective outgrowth of the peripheral axons of RB neurons by maintaining the expression of dpysl3.

Anomaly with no right ventral root at the seventh cervical segment in humans: gross anatomical and neuroanatomical study.

The cadaver of an 89-year-old woman who had died of cerebral apoplexy and which was dedicated to anatomy practice for medical students at Kumamoto University, was found to have complete lack of the right ventral root of the seventh cervical segment (C7). Observation of the peripheral spinal nerve indicated that the branch, which appeared to be a descending collateral of the ventral root of C6, became confluent with the dorsal root of C7 at the point just distal to the dorsal root ganglion. Following this confluence, new fiber elements ran out of the intervertebral foramen as the seventh cervical nerve. More peripherally, this fiber bundle joined the brachial plexus, its outward appearance was normal in the manner of ramification and each nerve's supply to muscles. Additionally, the inside view of the spinal cord of C6, C7 and C8 was examined neuroanatomically. Nissl staining of transverse sections at C7 (block 2) showed that motor neurons existed in the right anterior horn and their histological features were normal. Subsequently, horizontal sections were made from the two blocks, each of which contained C6/C7 (block 1) or C7/C8 (block 3), and were treated dually with Nissl and myelin staining. These sections also had a normal picture of cells and myelinated fibers on the right side as compared with those on the left side. The results suggested that motor neurons of the right C7 had a normal supply to the targets, although the trajectory of their axons in the spinal cord was obscure.

Ansa cervicalis as a variant of spinal accessory nerve plexus: a case report.

The ansa cervicalis is a neural loop in the neck formed by the union of two main nerve roots, namely superior and inferior roots, derived from ventral rami of the cervical nerves. With the expanding use of the ansa cervicalis for reinnervation procedures and the fact that it is located in the vicinity of major nerves and vessels of the neck, knowledge of the topography and morphology of this loop is quite necessary in the modern era. Any variation in the course, contributing roots or branching pattern of the ansa cervicalis, potentially alters and perhaps complicates the course of the procedures involving this nerve such as neurorrhaphy, skull base surgery, neck dissection, and anterior cervical spinal approach. Here, we present an unusual case of an ansa cervicalis encountered upon routine dissection of an adult male cadaver. In this case, the inferior root of the ansa cervicalis was formed by the joining of two rootlets, one originating from spinal accessory nerve and the other from a branch of the cervical plexus to the sternocleidomastoid muscle. The fibers traversing the branch of spinal accessory nerve were derived from the first segments of the cervical spinal cord. This case demonstrates a variant of the spinal accessory nerve plexus that contributed to the formation of the ansa cervicalis. Review of the literature was performed to reveal the possible clinical aspects of this anatomical variation.

Hes1 and Hes5 regulate the development of the cranial and spinal nerve systems.

The basic helix-loop-helix genes Hes1 and Hes5, known Notch effectors, regulate the maintenance of neural stem cells and the development of the central nervous system (CNS). In the absence of Hes1 and Hes5, the size, shape and cytoarchitecture of the CNS are severely disorganized, but the development of the peripheral nervous system remains to be analyzed. Here, we found that in Hes1;Hes5 double-mutant mice, the cranial and spinal nerve systems are also severely disorganized. In these mutant mice, axonal projections from the mesencephalic neurons to the trigeminal (V) ganglion become aberrant and the proximal parts of the glossopharyngeal (IX) and vagus (X) nerves are fused. The hypoglossal (XII) nerve is also formed poorly. Furthermore, the dorsal root ganglia are fused with the spinal cord, and the dorsal and ventral roots of the spinal nerves are lacking in many segments. These results indicate that Hes1 and Hes5 play an important role in the formation of the cranial and spinal nerve systems.

Mena and vasodilator-stimulated phosphoprotein are required for multiple actin-dependent processes that shape the vertebrate nervous system.

Ena/vasodilator-stimulated phosphoprotein (VASP) proteins regulate the geometry of the actin cytoskeleton, thereby influencing cell morphology and motility. Analysis of invertebrate mutants implicates Ena/VASP function in several actin-dependent processes such as axon and dendritic guidance, cell migration, and dorsal closure. In vertebrates, genetic analysis of Ena/VASP function is hindered by the broad and overlapping expression of the three highly related family members Mena (Mammalian enabled), VASP, and EVL (Ena-VASP like). Mice deficient in either Mena or VASP exhibit subtle defects in forebrain commissure formation and platelet aggregation, respectively. In this study, we investigated the consequence of deleting both Mena and VASP. Mena-/-VASP-/- double mutants die perinatally and display defects in neurulation, craniofacial structures, and the formation of several fiber tracts in the CNS and peripheral nervous system.

Short-time exposure to vinclozolin in utero induces testicular maldescent associated with a spinal nucleus alteration of the genitofemoral nerve in rats.

BACKGROUND/PURPOSE: Vinclozolin (V), a known antiandrogen, has been used widely to protect fruits, vegetables, and turf from fungus damage. The aim of this study was to clarify the effect of V on both the development of the spinal cord nucleus and testicular descent in rats. METHODS: Pregnant rats were administered 200 mg/kg/d of V from day 16 to 18 of gestation. At 5 days of age, the genitofemoral nerve (GFN) of male pups was identified on the psoas muscle, and diamidinophenyl indole was applied to the proximal cut end of the GFN. Forty-eight hours later, the T11 to L4 level of the spinal cord was removed, and 30-microm frozen serial sections were made. Next, the spinal nuclei labeled in a retrograde fashion by diamidinophenyl indole (DAPI) were examined with a fluorescence microscope. Additional male pups survived until 60 days of age to evaluate the position of the testes. RESULTS: The size of the DAPI-labeled spinal nuclei were smaller in the V-treated rats than in the control rats. The average number of the DAPI-labeled spinal nuclei decreased significantly more in the V-treated rats (176+/-33) than in the controls (247+/- 21; P <.05) during the newborn period. At 60 days of age, 15 of the 26 male rats showed either unilateral or bilateral undescended testes in the V-treated rats. The incidence of cryptorchidism was also significantly higher in the V-treated rats (57.7%) than in the controls (0%; P <.05). CONCLUSIONS: The antiandrogenic effect of the prenatal administration of V inhibited the development of the GFN nucleus in the spinal cord and induced testicular maldescent in rats. These results support the hypothesis that androgens regulate the descent of the testis through GFN development.

Absence of connections between spinal nerves and the spinal cord in a twin fetus: a very rare malformation occasionally evidenced at autopsy.

We describe a rare case of spinal cord malformation in a dichorionic diamniotic twin fetus aborted at 20 weeks' gestation due to acute chorioamnionitis with placental dysmaturity probably caused by a maternal viral infection. At autopsy, there were no connections between the spinal nerves and the spinal cord. The spinal cord lacked the posterior median fissure and gray matter; only a few neurons were present in the anterior and lateral gray columns. No chromosome anomalies were found. Although we cannot reconstruct the pathogenetic chain of events leading to this malformation, we believe that it is correlated with a maternal viral infection. We hypothesize that this viral infection altered the delicate balance between the factors inducing and those inhibiting fetal spinal neural differentiation.

Uncx4.1 is required for the formation of the pedicles and proximal ribs and acts upstream of Pax9.

The expression of the homeobox gene Uncx4.1 in the somite is restricted to the caudal half of the newly formed somite and sclerotome. Here we show that mice with a targeted mutation of the Uncx4.1 gene exhibit defects in the axial skeleton and ribs. In the absence of Uncx4.1, pedicles of the neural arches and proximal ribs are not formed. In addition, dorsal root ganglia are disorganized. Histological and marker analysis revealed that Uncx4.1 is not necessary for somite segmentation. It is required to maintain the condensation of the caudal half-sclerotome, from which the missing skeletal elements are derived. The loss of proximal ribs in Pax1/Pax9 double mutants and the data presented here argue for a role of Uncx4.1 upstream of Pax9 in the caudolateral sclerotome. Our results further indicate that Uncx4.1 may be involved in the differential cell adhesion properties of the somite.

Morphological alterations induced by sodium valproate on somites and spinal nerves in rat embryos.

The antiepileptic drug valproic acid is a well-known teratogenic agent; its main target organ is the neural tube, though skeletal malformations have also been described. In our recent work, respecifications of vertebrae were described in rat fetuses after treatment with 400 mg/kg of sodium valproate at specific somitogenic stages. The observed malformations were stage-dependent. Morphological segmental respecification was observed at the level of segments in formation at the moment of exposure and at the level of more posterior segments. Recently, specific alterations in the development of cranial nerves and ganglia were described in mouse embryos after in vitro exposure to VPA. The aim of the present work was to analyze dysmorphogenetic effects of VPA on embryonic metameric structures: somites, spinal and cranial nerves, and ganglia. Sodium valproate (400 mg/kg) was subcutaneously injected at specific gestational times corresponding to embryonic stages: presomitic or at about 2, 6, 10, 14, 18, or 22 somites. Females were sacrificed on the day 12 post coitum, and embryos were examined. Morphological examination of somites was performed by staining with acridine orange. Morphological examination of nerves and ganglia was performed by immunostaining, using monoclonal antibodies to the 160-kD neurofilament protein. No abnormalities were observed in the cranial nerves and ganglia. Specific and stage-dependent alterations were observed both at the level of the somites and at the level of the spinal nerves. The following characteristic malformations were observed: fusions, duplications, and reductions of somites and corresponding spinal nerves and ganglia. Our morphological data suggest a morphogenetic action of VPA at the level of the axial segments, with a possible respecification of the identity of the interested segments and their derivatives.

Unusual branching in lumbar plexus. Case report.

This article describes a complex bilateral variation in the formation of lumbar plexus in a 32 year old male cadaver. On the left side the plexus was postifixed and located posterior to the psoas major muscle. The femoral nerve was formed by the union of anterior rami of the second, third, fourth and fifth lumbar spinal nerves. On the right side, the lumbar plexus was prefixed. The lateral cutaneous nerve of the thigh was formed. By the union of the anterior rami of the first and second lumbar spinal nerves. The femoral nerve formed by branches from the first, second, third and fifth lumbar spinal nerves while the obturator nerve was formed by the union of the first, second and third lumbar spinal nerves. The right lumbar plexus was located in the substance of the psoas major muscle. In the present case, the formation of branches of the lumbar plexus were different from the previous data present in the literature.

Estenosis degenerativa del canal lumbar tratamiento quirurgico mediante recalibrado / Degenerative stenosis of lumbar space and surgical tratment by recalibration

Se presenta el caso de un paciente masculino de 62 anos, diagnosticado de estenosis degenerativa del canal lumbar, tratado quirurgicamente mediante la tecnica del recalibrado con buen resultado del tratamiento.

Abnormal course of spinal posterior roots and tracts associated with brain malformations. Sensory pathway malformation.

An unusual mode of the spinal posterior nerve root entrance and of the course of ascending tracts in the hyperplastic gray matter of the posterior horn was observed in three newborn babies. This "sensory pathway malformation" was combined with severe but unspecific brain anomalies. The common associated brain anomaly was agenesis of the corpus callosum.

[Peripheral nerve abnormalities of mutant (PMA) mouse--myelinated fiber counts of sciatic, peroneal, sural and tibial nerves].

A mutant mouse characterized by peroneal muscular atrophy and congenital absence of the peroneal nerve has been described by Esaki et al. and investigated as a possible animal model of Charcot-Marie-Tooth disease or spinal muscular atrophy. However, the nature of the peripheral nerve abnormality of this mutant mouse has not been precisely defined yet. In this study, in addition to the qualitative evaluation of teased fiber and Epon-embedded preparations, the total transverse fascicular area and the total numbers of myelinated fibers per nerve in sciatic, peroneal (proximal and distal), sural (proximal and distal) and tibial (proximal and distal) nerves on both right and left sides were compared between six peroneal muscular atrophy (pma) mice with autosomal recessive gene manifesting mainly the peroneal muscular atrophy and their six control mice to understand and define the peripheral nerve abnormalities. The pma mice showed pes equinovarus bilaterally and their peroneal nerves were absent. No myelinated fibers showing axonal degeneration or segmental demyelination were found on teased fiber preparation. Onion bulb, demyelinated or remyelinated axons and myelin ovoids were not observed in Epon-embedded sections. The mean total transverse fascicular area and mean total number of myelinated fibers per nerve in the sciatic nerve in pma mice was significantly less (p less than 0.02) than that in control mice. On the other hand they were significantly greater (p less than 0.0001) in the sural nerve in pma mice than in control mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Minor defects of the sacrum and neurogenic bladder dysfunction.

Minor defects of the sacrum are common and often dismissed as normal. The radiographs of 100 patients with urinary incontinence revealed sacral abnormalities in 43. Sacral evoked responses were measured and compared independently with the radiological findings. Patients who had defective closure of the dorsal neural arches of S1 or S2 all had abnormal nerve studies. We suggest that incomplete development of the bones of the dorsal neural arches of the upper sacrum may be a marker of incomplete neurogenesis of the sacral nerves. The sacral neurological deficit is subtle and difficult to demonstrate, but it is real and may be important in the pathogenesis of incontinence.

Anatomic and clinical studies of radicular symptoms.

Anatomic studies using cadavers showed that three factors are responsible for radicular symptoms. The first is congenital or acquired abnormalities of nerves and nerve roots--the intradural segmental arrangement of rootlets, congenital anomalies of the nerve roots, and the furcal nerve. Another factor is changes of bone and soft tissue around nerves and nerve roots--indentation of nerve roots and extremely transverse courses of nerve roots. The third factor is a correlation of two other factors--spatial relationship of the nervous tissue to osseous and nonosseous elements of the spinal canal and the intervertebral foramen. In the intervertebral foramen, the nerve root is surrounded by a rather thick membranous structure, an epiradicular sheath, which is responsible for a tubular form obtained in nerve root infiltration. Anatomic abnormalities can be observed in contrast studies, but the defects revealed do not correspond necessarily with neurologic symptoms. In such cases, nerve root infiltration is very useful for a functional diagnosis. The analysis of radicular symptoms with nerve root infiltration showed that radicular pain and/or claudication are caused mainly by single nerve root involvement, irrespective of the findings obtained by contrast studies. Furthermore, therapeutic effect of nerve root infiltration can be expected in any disease and it can be applied as a final trial of conservative treatment.