The ptotic tongue-imaging appearance and pathology localization along the course of the hypoglossal nerve

CT and MRI findings of tongue ptosis and atrophy should alert radiologists to potential pathology along the course of the hypoglossal nerve (cranial nerve XII), a purely motor cranial nerve which supplies the intrinsic and extrinsic muscles of the tongue. While relatively specific for hypoglossal nerve pathology, these findings do not accurately localize the site or cause of denervation. A detailed understanding of the anatomic extent of the nerve, which crosses multiple anatomic spaces, is essential to identify possible underlying pathology, which ranges from benign postoperative changes to life-threatening medical emergencies. This review will describe key imaging findings of tongue denervation, segmental anatomy of the hypoglossal nerve, imaging optimization, and comprehensive imaging examples of diverse pathology which may affect the hypoglossal nerve. Armed with this knowledge, radiologists will increase their sensitivity for detection of pathology and provide clinically relevant differential diagnoses when faced with findings of tongue ptosis and denervation.

Yin-Yang tongue sign: An imaging clue of lesions involving the skull base segment in the hypoglossal pathway

OBJECTIVE

To investigate the diagnostic value of the Yin-Yang tongue sign in patients with tongue deviation.

METHODS

According to the presence of the Yin-Yang tongue sign on CT/MR, 107 patients with tongue deviation were divided into a positive group and a negative group. The involvement categories of the hypoglossal canal (HC) in the positive group were evaluated and classified as HC dilation and HC erosion. The correlations between HC involvement categories and the presence of the sign were analysed.

RESULTS

There were 55 cases (55/107, 51.4%) in the positive group and 52 cases (52/107, 48.6%) in the negative group. Hypoglossal nerve (HN) involvement mainly occurred in the skull base (61.8%), skull base and carotid space (10.9%), and carotid space segment (12.7%). Neurogenic (50.9%), squamous cell carcinoma (14.5%), and metastases (12.7%) were the predominant aetiologies. The sensitivity, specificity, and accuracy of this sign for suggesting skull base lesions around HC were 72.4%, 80.8%, and 76.6%, respectively. In the positive group, HC dilation was seen in 21 patients (21/55, 38.2%) and 21 cases were all benign. HC erosion were noted in 19 patients (19/55, 34.5%), of whom 12 cases were malignant.

CONCLUSION

The Yin-Yang tongue sign is formed by unilateral tongue atrophy and fat infiltration caused by lesions in the HN pathway, especially compressive or invasive lesions involving the skull base segment.

Isolated Hypoglossal Nerve Palsy as an Early Symptom of a Granular Cell Tumor

Background: Hypoglossal nerve palsy (HNP) is rather common as a neurological disease. However, as an isolated nerve palsy it is an exceedingly rare phenomenon and points at local pathologies along the peripheral course of the nerve. In this communication we report a granular cell tumor (GCT) arising in the submandibular segment of the hypoglossal nerve. Case-Report: Spontaneous isolated HNP was recognized in a female patient. First line MR-imaging identified a clivus-chordoma. However, involvement of the hypoglossal nerve was highly unlikely according to MR-findings. Finally, ultrasonographic investigation revealed a small submandibular mass which, at histological examination, turned out to be a granular cell tumor arising within the hypoglossal nerve. Conclusions: This is the report of an extremely rare GCT originating within the 12th cranial nerve. The case illustrates that isolated motoric cranial nerve palsy may result from this rare tumor entity. This report also points out the diagnostic value of a simple ultrasonographic investigation to depict pathologic lesions of the submandibular space.

Respiratory pathology in the Optn-/- mouse model of Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disorder that results in death due to respiratory failure. Many genetic defects are associated with ALS; one such defect is a mutation in the gene encoding optineurin (OPTN). Using an optineurin null mouse (Optn^-/-), we sought to characterize the impact of optineurin deficiency on respiratory neurodegeneration. Respiratory function was assessed at 6 and 12 mo of age using whole body plethysmography at baseline during normoxia (FiO₂: 0.21; N₂ balance) and during a respiratory challenge with hypoxia and hypercapnia (FiCO₂: 0.07, FiO₂: 0.10; N₂ balance). Histological analyses to assess motor neuron viability and respiratory nerve integrity were performed in the medulla, cervical spinal cord, hypoglossal nerve, and phrenic nerve. Minute ventilation, peak inspiratory flow, and peak expiratory flow are significantly reduced during a respiratory challenge in 6 mo Optn^-/-mice. By 12 mo, tidal volume is also significantly reduced in Optn^-/- mice. Furthermore, 12mo Optn^-/- mice exhibit hypoglossal motor neuron loss, phrenic and hypoglossal dysmyelination, and accumulated mitochondria in the hypoglossal nerve axons. Overall, these data indicate that Optn^-/- mice display neurodegenerative respiratory dysfunction and are a useful model to study the impact of novel therapies on respiratory function for optineurin-deficient ALS patients.

[Occipital condyle syndrome as the first symptom of a metastatic hepatocellular carcinoma. Two case reports]

INTRODUCTION

Occipital condyle syndrome consists of the presence of unilateral occipital headache exacerbated by moving the head and is accompanied by paralysis of the ipsilateral hypoglossal nerve. One of its causes is infiltration of the base of the skull by bone metastases, especially those affecting the hypoglossal nerve due to infiltration as it passes through the osseous canal.

CASE REPORTS

We report two clinical cases of occipital condyle syndrome secondary to metastatic hepatocarcinoma. The first is that of a 52-year-old male with liver cirrhosis secondary to liver pathology caused by hepatitis C virus with occipital condyle syndrome as the presenting symptom in disseminated hepatocarcinoma. The second case is that of a 56-year-old male after recurrence of hepatocarcinoma following a liver transplant, despite not fulfilling the Milan criteria.

CONCLUSION

Occipital condyle syndrome is an alarm symptom and requires a thorough study by means of imaging tests, since it may be the first symptom of an undetected hepatocarcinoma.

Facilitation of distinct inhibitory synaptic inputs by chemical anoxia in neurons in the oculomotor, facial and hypoglossal motor nuclei of the rat

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the selective loss of motor neurons in the brainstem and spinal cord. Clinical studies have indicated that there is a distinct region-dependent difference in the vulnerability of motor neurons. For example, the motor neurons in the facial and hypoglossal nuclei are more susceptible to neuronal death than those in the oculomotor nucleus. To understand the mechanism underlying the differential susceptibility to cell death of the neurons in different motor nuclei, we compared the effects of chemical anoxia on the membrane currents and postsynaptic currents in different motor nuclei. The membrane currents were recorded from neurons in the oculomotor, facial and hypoglossal nuclei in brain slices of juvenile Wistar rats by using whole-cell recording in the presence of tetrodotoxin that prevents action potential-dependent synaptic transmission. NaCN consistently induced an inward current and a significant increase in the frequency of spontaneous synaptic inputs in neurons from these three nuclei. However, this increase in the synaptic input frequency was abolished by strychnine, a glycine receptor antagonist, but not by picrotoxin in neurons from the hypoglossal and facial nuclei, whereas that in neurons from the oculomotor nucleus was abolished by picrotoxin, but not by strychnine. Blocking ionotropic glutamate receptors did not significantly affect the NaCN-induced release facilitation in any of the three motor nuclei. These results suggest that anoxia selectively facilitates glycine release in the hypoglossal and facial nuclei and GABA release in the oculomotor nucleus. The region-dependent differences in the neurotransmitters involved in the anoxia-triggered release facilitation might provide a basis for the selective vulnerability of motor neurons in the neurodegeneration associated with ALS.

The Endoscopic Endonasal Approach to the Hypoglossal Canal: The Role of the Eustachian Tube as a Landmark for Dissection

IMPORTANCE

Improvements in endoscopic technology and reconstructive techniques have made the endoscopic endonasal approach (EEA) a viable option to approach ventromedial lesions in the region of the hypoglossal canal. Prior to contemplating this surgical corridor, a thorough understanding of anatomic relationships and landmarks is essential to safely approach this region of the posterior skull base through an EEA.

OBJECTIVE

To describe the surgical technique and anatomic landmarks in the EEA to the hypoglossal canal through referencing nasopharyngeal and posterior skull base anatomy.

DESIGN, SETTING, AND PARTICIPANTS

Study of latex-injected cadaveric heads at the North Carolina Eye Bank Multidisciplinary Surgical Skills Laboratory at the University of North Carolina.

INTERVENTIONS

An EEA to the hypoglossal canal was carried out bilaterally in 5 embalmed, latex-injected cadaver heads.

MAIN OUTCOMES AND MEASURES

Cadaveric measurements of anatomic landmarks and relationships in the approach were obtained using a 10-cm surgical ruler and were reported as mean distances. Additionally, high-quality endoscopic images demonstrating the operative technique and anatomic relationships were obtained.

RESULTS

The distance between the lacerum segment of the internal carotid arteries, the superolateral boundary, was 23.6 mm (SD, 11.8 mm). The distance between the anterolateral edge of the occipital condyles, the inferolateral boundary, was 19 mm (SD, 0.80 mm). The supracondylar groove was identified in the same anteroposterior plane as the nasopharyngeal orifice of the eustachian tube, and the anterior-most edge of the occipital condyle was 14 mm (SD, 0.82 mm) from the posterosuperior edge of the salpingopharyngeal fold. Additionally, the transtubercular corridor was on the same plane as the superior edge of the torus tubarius in the anteroposterior axis. The distance to the hypoglossal canal from midline was 10 mm, which was found after completing drilling in the transcondylar and transtubercular corridors. Last, the hypoglossal nerve rootlets were identified entering the canal 6 mm inferiorly and 8 mm laterally from the vertebrobasilar junction.

CONCLUSIONS AND RELEVANCE

The eustachian tube and other elements of nasopharyngeal anatomy are fixed landmarks that provide important points of reference when approaching the hypoglossal canal through an EEA. A thorough understanding of these anatomic relationships is vital in safely navigating this direct, surgical corridor to the posterior fossa.

Hypoglossal-facial nerve reconstruction using a Y-tube-conduit reduces aberrant synkinetic movements of the orbicularis oculi and vibrissal muscles in rats

The facial nerve is the most frequently damaged nerve in head and neck trauma. Patients undergoing facial nerve reconstruction often complain about disturbing abnormal synkinetic movements of the facial muscles (mass movements, synkinesis) which are thought to result from misguided collateral branching of regenerating motor axons and reinnervation of inappropriate muscles. Here, we examined whether use of an aorta Y-tube conduit during reconstructive surgery after facial nerve injury reduces synkinesis of orbicularis oris (blink reflex) and vibrissal (whisking) musculature. The abdominal aorta plus its bifurcation was harvested (N = 12) for Y-tube conduits. Animal groups comprised intact animals (Group 1), those receiving hypoglossal-facial nerve end-to-end coaptation alone (HFA; Group 2), and those receiving hypoglossal-facial nerve reconstruction using a Y-tube (HFA-Y-tube, Group 3). Videotape motion analysis at 4 months showed that HFA-Y-tube group showed a reduced synkinesis of eyelid and whisker movements compared to HFA alone.

[Neuritis cordis and myocarditis in rabies]

Once the rabies virus has spread through the central nervous system (CNS), the virus is also transported centrifugally along axons, especially of the autonomic nervous system, to a wide range of organs including the heart. In this case report of a 49-year-old man who had been bitten by a dog in Asia, the rabies infection of cardiac nerves and cardiac muscle fibres is shown by immunohistochemistry. The neuritis cordis and rabies myocarditis can have important clinical effects on the heart rate and myocardial function and lead to blood pressure crises which are typical for the clinical course of rabies in humans.

Hypoglossal schwannoma-successful reinnervation and functional recovery of the tongue following tumour removal and nerve grafting

OBJECTIVE

Hypoglossal nerve schwannomas are rare tumours that usually cause ipsilateral hypoglossal palsy. This report describes such lesions in two patients and suggests nerve grafting as part of the treatment regimen.

METHOD

Two patients with intra- and extra-dural hypoglossal schwannomas respectively were treated by direct surgery via a postero-lateral approach to the posterior fossa, hypoglossal canal and carotid sheath. Following tumour removal, sural nerve grafting was used to reconstruct the nerves. Unexpectedly, muscle bulk and motor function returned within 6 months in both patients.

CONCLUSION

Nerve grafting was highly successful in achieving functional recovery following surgery for hypoglossal nerve schwannomas.

Oestradiol rapidly enhances spontaneous glycinergic synaptic inhibition of hypoglossal motoneurones

Whereas oestradiol is well-known to facilitate excitatory glutamatergic synaptic transmission, its effects on fast inhibitory neurotransmission are not as well established. Possible acute modulation of the spontaneous glycinergic synaptic activity by oestradiol was investigated in voltage-clamped hypoglossal motoneurones by whole-cell patch-clamp recording in rat brainstem slices. The spontaneous glycinergic synaptic activity was continuously recorded in each neurone under control conditions, during 12-20 min of perfusion with 17beta-oestradiol and during washing. When oestradiol was diluted in ethanol, the control solution contained the same amount of ethanol. At 100 nM, oestradiol markedly increased the frequency of the total spontaneous glycinergic activity. Similar experiments were performed after blockade of action potentials by tetrodotoxin, aiming to isolate miniature glycinergic synaptic currents. Oestradiol increased the frequency of glycinergic miniatures in most slices, in some cases within less than 1 min. In some slices, oestradiol also favoured the occurrence of glycinergic miniatures of large amplitude. These effects were slowly reversible during washing. At 1 nm, oestradiol still increased the frequency of glycinergic miniatures. The results were confirmed in the absence of ethanol by using water-soluble cyclodextrin-encapsulated oestradiol. In these experiments, the control solution contained the same amount of (2-hydroxypropyl)-beta-cyclodextrin as the oestradiol-containing solution. In addition, prolonged control recordings were performed without applying oestradiol to check the stability of the glycinergic synaptic activity during prolonged whole-cell recordings. The results show, for the first time, that, within a few minutes, oestradiol can enhance the spontaneous synaptic release of a major inhibitory transmitter, glycine.

Facial reanimation by means of the hypoglossal nerve: anatomic comparison of different techniques

OBJECTIVE

The goal of this study was to determine the various anatomical and surgical relationships between the facial and hypoglossal nerves to define the required length of each for a nerve transfer, either by means of a classical hypoglossal-facial nerve anastomosis or combined with any of its variants developed to reduce tongue morbidities.

METHODS

Five adult cadaver heads were bilaterally dissected in the parotid and submaxillary regions. Two clinical cases are described for illustration.

RESULTS

The prebifurcation extracranial facial nerve is found 4.82 +/- 0.88 mm from the external auditory meatus, 5.31 +/- 1.50 mm from the mastoid tip, 15.65 +/- 0.85 mm from the lateral end of C1, 17.19 +/- 1.64 mm from the border of the mandible condyle, and 4.86 +/- 1.29 mm from the digastric muscle. The average lengths of the mastoid segment of the facial nerve and the prebifurcation extracranial facial nerve are 16.35 +/- 1.21 mm and 18.93 +/- 1.41 mm, respectively. The average distance from the bifurcation of the facial nerve to the hypoglossal nerve turn is 31.56 +/- 2.53 mm. For a direct hypoglossal-facial nerve anastomosis, a length of approximately 19 mm of the hypoglossal nerve is required. For the interposition nerve graft technique, a 35 mm-long graft is required. For the technique using a longitudinally dissected hypoglossal nerve, an average length of 31.56 mm is required. Exposure of the facial nerve within the mastoid process drilling technique requires 16.35 mm of drilling.

CONCLUSION

This study attempts to establish the exact graft, dissection within the hypoglossal nerve, and mastoid drilling requirements for hypoglossal to facial nerve transfer.

Inhibition of resting potassium conductances by long-term activation of the NO/cGMP/protein kinase G pathway: a new mechanism regulating neuronal excitability

Glutamate-induced excitotoxicity, the most common pathological mechanism leading to neuronal death, may occur even with normal levels of glutamate if it coincides with a persistent enhancement of neuronal excitability. Neurons expressing nitric oxide (NO) synthase (NOS-I), which is upregulated in many human chronic neurodegenerative diseases, are highly susceptible to neurodegeneration. We hypothesized that chronic production of NO in damaged neurons may increase their intrinsic excitability via modulation of resting or "leak" K+ currents. Peripheral XIIth nerve injury in adult rats induced de novo NOS-I expression and an increased incidence of low-threshold motor units, the latter being prevented by chronic inhibition of the neuronal NO/cGMP pathway. Accordingly, sustained synthesis of NO maintained an enhanced basal activity in injured motoneurons that was slowly reverted (over the course of 2-3 h) by NOS-I inhibitors. In slice preparations, persistent, but not acute, activation of the NO/cGMP pathway evoked a robust augment in motoneuron excitability independent of synaptic activity. Furthermore, chronic activation of the NO/cGMP pathway fully suppressed TWIK-related acid-sensitive K+ (TASK) currents through a protein kinase G (PKG)-dependent mechanism. Finally, we found evidence for the involvement of this long-term mechanism in regulating membrane excitability of motoneurons, because their pH-sensitive currents were drastically reduced by nerve injury. This NO/cGMP/PKG-mediated modulation of TASK conductances might represent a new pathological mechanism that leads to hyperexcitability and sensitizes neurons to excitotoxic damage. It could explain why de novo expression of NOS-I and/or its overexpression makes them susceptible to neurodegeneration under pathological conditions.

Peripheral nerve injury induced expression of mRNA for serine protease inhibitor 3 in the rat facial and hypoglossal nuclei but not in the spinal cord

The current work has documented the expression of the mRNAs for serine protease inhibitor 3 (SPI-3) in the facial and hypoglossal nuclei following peripheral nerve transection by using the in situ hybridization method. The signals appeared 6 hour after nerve injury; they became stronger on day 1 of injury and persisted for 21 days. SPI-3 may be involved during early events of modulating the activities of serine proteases following nerve injury. Such activities may include synaptic stripping and re-organization and facilitation of glial cell reaction to nerve injury. In the later stages of nerve injury SPI-3 may enhance neuronal survival, growth of neurites and re-establishment of synaptic contacts in the facial and hypoglossal nuclei. Hypoglossal but not facial nerve transection caused the expression of mRNAs for SPI-3 in the pineal gland. The signals appeared 6 hours after nerve injury and persisted for 21 days. The significance of this observation is not known but it indicates that the pineal gland senses injury to some peripheral nerves including the hypoglossal nerve. The study has also showed that axotomy of the sciatic nerve did not give rise to the up-regulation of the mRNAs for SPI-3 in the spinal cord. There was no hybridization signals in the lumbar segments; an indication that SPI-3 may not form part of molecules that are released during sciatic nerve transaction by the neural and non-neural cells of the spinal cord. At the moment there are no antibodies for SPI-3 and therefore future studies are needed to verify the findings. It will be interesting also to study on the role of pineal gland during peripheral nerve injuries.

Implications of ALS focality: rostral-caudal distribution of lower motor neuron loss postmortem

BACKGROUND

Because motor manifestations of ALS begin focally and progress contiguously, the anatomic distribution of underlying lower motor neuron and upper motor neuron degeneration should correlate to onset.

OBJECTIVES

To assess the rostral-caudal distribution of lower motor neuron loss in relation to the region of clinical onset.

METHODS

We evaluated 19 ALS postmortem nervous systems from patients whose motor manifestations had begun in different body regions. In each, we looked at four neuraxis levels: hypoglossal nucleus and cervical, thoracic, and lumbar spinal cord. We used light microscopy and devised a technique of particle counting that indexed lower motor neuron loss.

RESULTS

The average overall loss of lower motor neurons in ALS nervous systems was 55%, and the range of loss had a normal distribution that ranged between 8% and 90%. The distribution of lower motor neuron loss was graded within the nervous system relative to onset (p = 0.02 by analysis of variance). In 14 of the 19 nervous systems, the regional lower motor neuron loss within the nervous systems was graded radially away from the region of onset. In 1, radial degeneration seemed likely but did not meet significance. In 2, radial degeneration was apparent but loss was greatest in a region different than that identified as the region of onset. In the remaining 2, lower motor neuron loss was minimal and not graded (both from patients whose motor manifestations had been predominantly upper motor neuron).

CONCLUSION

Lower motor neuron degeneration in ALS is a focal process that advances contiguously, summates over time, and creates graded loss. Stage of degeneration in the nervous system is a function of anatomic location.

Medullary microvessel degeneration in multiple system atrophy

Multiple system atrophy (MSA) is a rare and fatal early-onset autonomic disorder which is characterised by Parkinsonism and orthostatic hypotension (OH). The pathophysiology of MSA is not fully understood but key features include the depletion of medullary autonomic neurons and presence of glial cellular inclusions. We hypothesise that the degeneration of medullary autonomic microvessels is an additional finding in MSA. Using digital pathology we quantified basement membrane collagen (Coll IV), smooth muscle actin (alpha-actin) and endothelial glucose transporter (Glut 1) expression in medullary autonomic nuclei of 8 MSA and 8 OH cases, compared with 12 controls with no autonomic dysfunction. We found decreased Coll IV (p=0.000) and Glut 1 (p=0.000) but not alpha-actin expression, in medullary autonomic nuclei of MSA, but not OH cases compared with control subjects. Medullary microvessel degeneration in MSA may be secondary to the primary neuro-glial pathogenesis of the disorder, and could accelerate its ageing-related progression.

The midline suboccipital subtonsillar approach to the hypoglossal canal: surgical anatomy and clinical application

Primary lesions of the hypoglossal canal, such as hypoglossal schwannomas, are rare. No consensus exists with regard to the surgical approach of choice for treatment of these lesions. Usually, lateral transcondylar approaches have been used. The authors describe the surgical anatomy of the midline subtonsillar approach to the hypoglossal canal. This approach includes a midline suboccipital craniotomy, dorsal opening of the foramen magnum and elevation of ipsilateral cerebellar tonsil to expose the hypoglossal nerve and its canal. The midline subtonsillar approach permits a straight primary intradural view to the hypoglossal canal. There is no necessity of condylar resections. The surgical anatomy of the subtonsillar approach is described and illustrated by an example of a case.

[Neurilemmoma of the head and neck--report of 3 cases]

BACKGROUND

Neurilemmoma are benign tumors of the nerve-sheath, also known as schwannoma. Beside intracranial manifestation, neurilemmoma are found at other peripheral nerves of the head and neck.

CASE REPORT

We present three cases of patients with seldom manifestation of neurilemmoma of the supraglottis, the retropharyngeal space and a neurilemmoma of the hypoglossal nerve. The histological examination showed two types of Antoni-A-neurilemmoma, whereas one tumor was found with mixed type A and B-neurilemmoma.

CONCLUSION

Although extracranial neurilemmoma of retropharygeal space, neck or supraglottic larynx are rare tumors, neurilemmoma should be involved in differential diagnosis of tumors in these areas. The therapy of choice consists of complete surgical removal and histological examination.

Unusual presentations of craniovertebral junction tuberculosis: a report of 2 cases and literature review

BACKGROUND

CVJ tuberculosis is a described entity requiring challenging ways of management. Severe neck pain, causing restricted neck movements and torticollis, is a characteristic presentation of neurologically asymptomatic suboccipital Pott's disease.

CASE DESCRIPTION

Two patients with unusual CVJ tuberculosis form the basis for the present communication. The first patient presented with tubercular otitis media, causing progressive erosion of the petrous part of temporal bone, and destruction of the occipital condyle, along with the lateral mass of atlas, leading to CVJ instability. This is a first report of such a presentation, according to our knowledge. Detailed bony architectural destruction demonstrable on CT scan has been described. The second patient, with CVJ tuberculosis, presented with skull base syndrome and with multiple cranial nerve palsies. Both patients were managed without surgical intervention and showed clinical and radiological recovery.

CONCLUSION

In such patients with unusual clinical presentations, histopathologic examination is necessary to arrive at a correct diagnosis. The management of patients with tubercular involvement of CVJ remains controversial. In the present communication, both the patients were managed successfully with full dose of antitubercular drugs and immobilization.

Side-to-end hypoglossal-facial anastomosis via transposition of the intratemporal facial nerve

The technique of facial nerve repair with side-to-end hypoglossal-facial anastomosis is presented and evaluated in five patients who were operated on for facial nerve paralysis after acoustic schwannoma surgery, or had cranial base trauma. The end-to-end hypoglossal-facial anastomosis is accompanied by hemilingual paralysis, with difficulty in swallowing, chewing and speaking. In this new technique, the facial nerve is mobilised in the temporal bone, transected at the second genu and transposed to the hypoglossal nerve where a tensionless side-to-end anastomosis is performed. The hypoglossal nerve is transected in oblique fashion to about one third of its circumference. We were able to achieve a tensionless anastomosis in all patients. The idea is to bring about re-innervation of the previously denervated tissue via a collateral sprouting of axons of the donor nerve through the site of coaptation without sacrificing the innervation of the donor nerve's original targets. With side-to-end hypoglossal-facial anastomosis, two patients attained a House- Brackmann grade of III (one of them with independent movement of eyelids and mouth); one achieved grade IV, another grade V and grade VI. No patient had hemilingual atrophy nor any problems associated with swallowing or chewing.

Usefulness of transcervical approach for surgical treatment of hypoglossal schwannoma with paraspinal extension: case report

BACKGROUND

Usefulness of transcervical approach to hypoglossal schwannoma with paraspinal extension is described herein.

CASE DESCRIPTION

A 54-year-old woman presented with gradually worsening left hypoglossal nerve palsy. The findings were of a tumor lying in the left hypoglossal canal and paraspinal region and were consistent with hypoglossal schwannoma. Subtotal intracapsular removal of the tumor was performed via transcervical approach. The symptoms improved, and no additional symptoms were noted.

CONCLUSION

The transcervical approach and intracapsular removal of the tumor under electrophysiological monitoring provided for successful minimally invasive surgery in this case of hypoglossal schwannoma.

Hypoplasia and neuronal immaturity of the hypoglossal nucleus in sudden infant death

OBJECTIVE

To report the case of five month old female baby with a history of episodes of gastro-oesophageal reflux and pneumonia. Her sudden death offered a unique insight into the possible role of delayed neuronal maturation and hypoplasia of the hypoglossal nucleus in representing a likely morphological substrate of sudden death.

METHODS

Morphometric analysis was carried out with an Image-Pro Plus Image analyser (Media Cybernetics) on both sides of the brain stem.

RESULTS

Hypoplasia and neuronal immaturity of the hypoglossal nucleus were demonstrated, accompanied by hypoplasia of the arcuate nucleus.

CONCLUSIONS

Much attention should be paid to the possible role of the hypoglossal nucleus in determining a lethal outcome in infancy through impairment of deglutition and subsequent recurrent episodes of pneumonia, and as a necropsy finding.

Effects of hypoglossal and facial nerve injuries on milk-suckling

Functional roles of the perioral anatomical structures involved in breastfeeding were examined in newborn rat pups in which the hypoglossal (XII) and facial (VII) nerves had been resected at the neonatal stage. The XII nerve controls tongue movement and is comprised of two functionally distinct branches: the medial branch related to protrusion of the tongue and the lateral branch related to its retraction. Newborn rat pups with bilateral resection of either of the XII nerve components (main trunk: XII-trunk; medial branch: XII-med; lateral branch: XII-lat) failed to suckle milk and did not survive. Unilateral XII nerve-resected neonates showed different milk-suckling capabilities, which thus resulted in differences in survival rate (XII-trunk: 38%; XII-med: 24%; XII-lat: 92%) and postnatal growth during the postnatal 3 weeks until P21. Unilateral and bilateral resections of the VII nerve innervating the buccolabial musculature produced lowered suckling capabilities and retarded postnatal growth, although all pups showed 100% survival. The results indicate a crucial role of the tongue, especially of protruding muscular elements innervated by the XII-med nerve, in breastfeeding. The results also indicate differential effects of the VII and XII nerve components on suckling capability, survival, and postnatal growth of newborn rat pups.

Endoscope-assisted microsurgical resection of an intraneural ganglion cyst of the hypoglossal nerve

✓ An unusual case of an intraneural ganglion cyst of the hypoglossal nerve is presented. Only one case of this rare clinical entity has been reported previously. A 51-year-old woman presented with a 6-month history of left-sided hypoglossal nerve palsy. Magnetic resonance imaging revealed a cystic lesion related to the hypoglossal canal. There was no enhancement of the lesion after administration of Gd. A high-resolution computerized tomography scan of the skull base demonstrated an enlargement of the hypoglossal canal.

To access the lesion, a far-lateral endoscope-assisted microsurgical approach was used. An intraneural ganglion lesion invading the hypoglossal nerve was found and resected. A histopathological examination confirmed that the lesion was an intraneural ganglion cyst. The occurrence of an intraneural ganglion cyst at the hypoglossal nerve is very rare. This case exemplifies an atypical location of a synovial cyst with cranial nerve involvement.

Expression of Reg/PAP family members during motor nerve regeneration in rat

In this study, we examined the expression of mRNAs for Regenerating gene (Reg)/pancreatitis-associated protein (PAP) family members following hypoglossal nerve injury in rats. In addition to four rat family members (RegI, Reg-2/PAP I, PAP II, and PAP III) that had been identified, we newly cloned and sequenced a type-IV Reg gene in rats. Among these five family members, the expression of Reg-2/PAP I mRNA was predominantly enhanced in injured motor neurons after axotomy. Furthermore, a marked induction of PAP III mRNA was observed in the distal part of the injured nerve. A polyclonal antibody was raised against PAP III, and a Western blotting analysis using this antibody confirmed an increased level of PAP III protein in the injured nerve. These results suggest that Reg family members would be new mediators among injured neurons and glial cells, and may play pivotal roles during nerve regeneration.

Adult motor neurons show increased susceptibility to axotomy-induced death in mice lacking clusterin

Clusterin is a highly conserved, amphiphatic glycoprotein present in most tissues. It has been shown to be involved in the regulation of lipid transportation, clearance of cellular debris from the extracellular space and intracellular signal transduction. Clusterin is markedly up-regulated after neural injury but the functional significance of this response is unclear. Here, we show that clusterin up-regulation is substantially greater in hypoglossal motor neurons after hypoglossal nerve avulsion compared with nerve transection. Quantitative analyses of motor neuron numbers after the same lesions in clusterin(-/-) and clusterin(+/+) mice showed significantly larger numbers of surviving motor neurons in clusterin(+/+) mice. These results suggest that clusterin has a neuroprotective role after axotomy.

Mouse model for ablation of proliferating microgliain acute CNS injuries

Activation of microglia, the primary immune effectors of the CNS and proinflammatory signaling, is a hallmark of brain damage. However, it remains controversial whether microglial cells have beneficial or detrimental functions in various neuropathological conditions. We report the generation of transgenic mice that express a mutant form of herpes simplex virus type 1 thymidine kinase (HSV-1 TK(mt-30)) driven by the myeloid-specific CD11b promoter. Using two paradigms of nervous system damage, hypoglossal nerve axotomy, and cortical stab injury, we show that specific ablation of proliferating microglia in CD11b-TK(mt-30) mice can be achieved by administration of ganciclovir. For example, after hypoglossal nerve injury, a 75% reduction in proliferating microglial cells was observed at the site of injury. The CD11b-TK(mt-30) transgenic mouse should provide a valuable tool for studying the role of microglia in CNS damage and repair.

Tapia's syndrome following septorhinoplasty

No surgery is free of complications varying from common minor problems to very unexpected and severe ones. In the case presented here, unilateral paralysis of the muscles of the tongue and ipsilateral vocal cord paralysis due to a lesion of the 10th and 12th cranial nerves occurred following a septorhinoplasty that was performed under endotracheal general anesthesia. This rare entity known as Tapia's Syndrome is believed to be caused by pressure neuropathy of both nerves due to inflation of the cuff within the larynx. We remind surgeons of this unusual complication that can occur in any surgery under general anesthesia and discuss its diagnosis, treatment method, and the followup results in light of the literature.

Regulation of stearoyl-CoA desaturase-1 after central and peripheral nerve lesions

Background

Interruption of mature axons activates a cascade of events in neuronal cell bodies which leads to various outcomes from functional regeneration in the PNS to the failure of any significant regeneration in the CNS. One factor which seems to play an important role in the molecular programs after axotomy is the stearoyl Coenzyme A-desaturase-1 (SCD-1). This enzyme is needed for the conversion of stearate into oleate. Beside its role in membrane synthesis, oleate could act as a neurotrophic factor, involved in signal transduction pathways via activation of protein kinases C.

Results

In situ hybridization and immunohistochemistry demonstrated a strong up-regulation of SCD at mRNA and protein level in regenerating neurons of the rat facial nucleus whereas non-regenerating Clarke's and Red nucleus neurons did not show an induction of this gene.

Conclusion

This differential expression points to a functionally significant role for the SCD-1 in the process of regeneration.

Critical role for DP5/Harakiri, a Bcl-2 homology domain 3-only Bcl-2 family member, in axotomy-induced neuronal cell death

The survival of neurons is maintained primarily by neurotrophic factors that suppress the apoptotic program. Axotomy or removal of peripheral targets causes neuronal cell death, but the mechanisms involved in the induction of this type of cell death remain poorly understood. Here, we show that DP5/Harakiri, a Bcl-2 homology domain 3-only member of the Bcl-2 family, is induced in motoneurons after transection of the hypoglossal nerve in mice and in sympathetic neurons after nerve growth factor (NGF) withdrawal. To assess the role of DP5 in neuronal cell death, mutant mice deficient in DP5 were generated by gene targeting. DP5-/- mice were viable and exhibited normal postnatal development. Notably, motoneurons from DP5-/- mice were highly protected from cell death induced by resection of the hypoglossal nerve compared with motoneurons from DP5+/+ littermate mice. In addition, deficiency of DP5 in superior cervical ganglia (SCG) neurons resulted in delayed neuronal cell death triggered by NGF withdrawal. Analysis of SCG neurons from DP5-/- mice revealed increased preservation of mitochondrial membrane potential and reduced activation of caspase-3 compared with neurons from wild-type mice. These results indicate that DP5 plays an important role in neuronal cell death induced by axotomy and NGF deprivation through the regulation of mitochondrial function and caspase-3 activation.

Exophytic pilocytic astrocytoma of the brain stem in an adult with encasement of the caudal cranial nerve complex (IX?XII): presurgical anatomical neuroimaging using MRI

We describe a rare case of adult pilocytic astrocytoma in which exophytic growth from the brain stem presented as a right cerebellopontine angle mass. An initial MRI examination using T2- and T1-weighted images without and with contrast suggested the diagnosis of schwannoma. Subsequent use of 3D CISS (three-dimensional constructive interference in steady state) and T1-weighted contrast-enhanced 3D MP-RAGE (three-dimensional magnetization prepared rapid acquisition gradient echo) sequences led to the diagnosis of an exophytic brain stem tumor, documented the precise relationships of the tumor to cranial nerve VIII, revealed encasement of cranial nerves IX-XII (later confirmed intraoperatively), and provided the proper basis for planning surgical management.

[Neuropsychological and scintigraphic aspects of frontotemporal dementia preceding amyotrophic lateral sclerosis]

Between 1993 and 2001, we observed fifteen patients (ten men and five women, mean age 63 years) with frontotemporal dementia (FTD) which preceded signs of amyotrophic lateral sclerosis (ALS) which developed 21 months later. Mean disease duration in the fourteen deceased patients was 38 months. FTD associated with ALS is characterized by rapid course, predominance of disinhibited forms (orbito-basal), presence of aphasia with neologisms, and semantic memory disorders. Performed in all patients, single-photon emission computed tomography demonstrated a bifrontal pattern of low uptake, sometimes associated with low uptake in the anterior temporal region. In one patient, neuropathology revealed neuron atrophy and loss in the frontotemporal region, the anterior horns, and the hypoglossal nucleus. Ubiquitin-positive inclusions were visible in the dentate gyrus of the hippocampus and in the anterior horns. The dementia/ALS association is classically described is uncommon. It belongs to the FTD group since the Lund and Manchester consensus. Approximately 15 p.100 of patient with FTD can be expected to develop ALS. About 250 cases have been reported in the literature, half of them in the Pacific area where the incidence of ALS is high (55/100,000 inhabitants versus 1/100,000 in the rest of the world). Intermediary forms of FTD, semantic dementia, and progressive non-fluent aphasia are discussed since several cases of non-fluent progressive aphasia associated with ALS are reported in the literature. The links between these two degenerative diseases are discussed.

Subacute mandibular and hypoglossal nerve denervation causing oedema of the masticator space and tongue

We report the MRI of five patients with denervation oedema in the head and neck. Four had denervation oedema in one masticator space caused by a skull-base tumour invading the ipsilateral foramen ovale. Another case had denervation oedema confined to the half of the tongue ipsilateral to oral reconstruction surgery which involved mandibulectomy, free flap repair and wide excision of a buccal mucosal carcinoma. Inversion-recovery and/or T2-weighted spin-echo images showed increased signal in the affected areas. Contrast-enhanced T1-weighted images revealed enhancement of the muscles. There was no evidence of tumour or infection in the masticator space or tongue. It is important to differentiate denervation oedema from other disease processes causing high signal on T2-weighted images, such as tumour infiltration and soft-tissue infection.

Solitary fibrous tumor of the hypoglossal nerve

SUMMARY

We report a case of solitary fibrous tumor (SFT) causing isolated hypoglossal nerve palsy. The neuroimaging appearance of the tumor was indistinguishable from that of schwannoma or meningioma. Immunohistochemical tests demonstrated strong reactivity for CD34 but an absence of staining for S100 and epithelial membrane antigen; this profile is indicative of an SFT. SFTs are mesenchymal tumors that can affect the dura-covered segments of cranial nerves. They may be considered in the differential diagnosis of an isolated cranial nerve palsy.

Rapid prion neuroinvasion following tongue infection

Food-borne transmission of prions can lead to infection of the gastrointestinal tract and neuroinvasion via the splanchnic and vagus nerves. Here we report that the transmission of transmissible mink encephalopathy (TME) is 100,000-fold more efficient by inoculation of prions into the tongues of hamsters than by oral ingestion. The incubation period following TME agent (hereinafter referred to as TME) inoculation into the lingual muscles was the shortest among the five nonneuronal routes of inoculation, including another intramuscular route. Deposition of the abnormal isoform of the prion protein, PrP(Sc), was first detected in the tongue and submandibular lymph node at 1 to 2 weeks following inoculation of the tongue with TME. PrP(Sc) deposits in the tongue were associated with individual axons, and the initial appearance of TME in the brain stem was found in the hypoglossal nucleus at 2 weeks postinfection. At later time points, PrP(Sc) was localized to brain cell groups that directly project to the hypoglossal nucleus, indicating the transneuronal spread of TME. TME PrP(Sc) entry into the brain stem preceded PrP(Sc) detection in the rostral cervical spinal cord. These results demonstrate that TME can replicate in both the tongue and regional lymph nodes but indicate that the faster route of brain invasion is via retrograde axonal transport within the hypoglossal nerve to the hypoglossal nucleus. Topical application of TME to a superficial wound on the surface of the tongue resulted in a higher incidence of disease and a shorter incubation period than with oral TME ingestion. Therefore, abrasions of the tongue in livestock and humans may predispose a host to oral prion infection of the tongue-associated cranial nerves. In a related study, PrP(Sc) was detected in tongues following the intracerebral inoculation of six hamster-adapted prion strains, which demonstrates that prions can also travel from the brain to the tongue in the anterograde direction along the tongue-associated cranial nerves. These findings suggest that food products containing ruminant or cervid tongue may be a potential source of prion infection for humans.

Differential vulnerability of cranial motoneurons in mouse models with motor neuron degeneration

Amyotrophic lateral sclerosis (ALS) is characterized by the progressive degeneration of selective motoneuron populations, yet it remains unclear why some groups of motoneurons are more vulnerable than others. Our aim was to compare the motoneuron loss in five cranial nuclei at different stages of the disease in three mouse models of ALS: two naturally occurring murine models (progressive motor neuronopathy (pmn) and wobbler) and a transgenic mouse model with a human G93A mutation in the superoxide dismutase-1 (SOD1) gene. By quantifying these different motoneuron populations we report that the degree of degeneration in the various cranial motoneuron nuclei depends on the mouse model and the stage of the disease. The biologically most significant difference between the mutations occurs in the oculomotor/trochlear nucleus which is affected in the pmn mouse but not in the wobbler and SOD G93A mice. These results suggest that there is a selective degeneration of cranial motoneurons in these mouse models as in ALS patients.

Hypoglossal neurinoma presenting with intratumoral hemorrhage

Focal or microscopic hemorrhage in a neurinoma is common, but tumor origin from the hypoglossal nerve and extensive symptomatic intratumoral hemorrhage are both rare. A 59-year-old male presented with severe neck pain, nausea and vomiting of 1-day duration, accompanied by right hypoglossal nerve palsy. Neuroimaging disclosed a tumor located in the right cerebellomedullary fissure and containing a hematoma. The right hypoglossal canal was slightly dilated. The intracranial tumor was resected via a suboccipital approach. Histological examination demonstrated spindle-shaped tumor cells with nuclear palisading and also relative hypervascularity with hyaline degeneration of the vessels. Extensive hemorrhage was present, as was necrosis. Thickening and hyalinization of arterial walls, a common occurrence in neurinomas, may have contributed to symptomatic intratumoral hemorrhage.

Imaging of the lower cranial nerves

Knowledge of the nuclear origins and the normal course of the cranial nerves, and their functional components, is important in any evaluation of cranial neuropathy. MR imaging allows detailed evaluation of cranial nerve anatomy and pathology. Newer MR sequences allow more sensitive methods of detecting pathology and determining the cause of cranial neuropathy. The correlation of clinical findings with MR images will allow for more definitive evaluation.

The relationship between Bunina bodies, skein-like inclusions and neuronal loss in amyotrophic lateral sclerosis

Specific pathological hallmarks have been described in amyotrophic lateral sclerosis (ALS), which include motor neuronal loss, Bunina bodies (BBs) and skein like inclusions (SLIs). We investigated the relation between these three lesions in the cervical and lumbar anterior horns and the hypoglossal nuclei of 20 ALS patients and 9 controls using a quantitative light microscopy study. Immunohistochemistry with anti-cystatin C and anti-ubiquitin was used to detect the BBs and SLIs, respectively. A significant relation between the severity of neuronal loss and the proportion of SLI-containing neurons was found in the spinal cord, whereas no relation was found with BBs. We therefore propose that BBs and SLIs participate in two different steps of the cascade leading to neuronal loss.

Detailed anatomy of the intracranial segment of the hypoglossal nerve: neurovascular relationships and landmarks on magnetic resonance imaging sequences

OBJECT

The thin hypoglossal nerve can be very difficult to distinguish on magnetic resonance (MR) images. The authors used a combination of sequences to increase the reliability of MR imaging in its demonstration of the 12th cranial nerve as well as to assess the course of the nerve, display its relationships to adjacent vessels, and provide landmarks for evaluating the nerve in daily practice.

METHODS

The study group consisted of 34 volunteers (68 nerves) in whom a three-dimensional (3D) Fourier-transformation constructive interference in steady-state (CISS) sequence and a 3D T1-weighted contrast-enhanced magnetization-prepared rapid-acquisition gradient-echo (MPRAGE) sequence were applied. Two trained neuroradiologists collaboratively identified the hypoglossal trigone, preolivary sulcus, 12th cranial nerve, posterior inferior cerebellar artery, vertebral artery, 12th nerve root sleeve, and the hypoglossal canal on each side. The 3D CISS sequence successfully demonstrated the hypoglossal trigone (100% of images), 12th nerve root bundles (100% of images), and 12th nerve sleeves (88.2% of images). The canalicular segment was exhibited with the aid of plain 3D CISS sequences in 74% of images and by using contrast-enhanced 3D CISS sequences and contrast-enhanced MPRAGE sequences in 100% of images. The landmarks that proved useful to identify the cisternal segment of the 12th cranial nerve included the hypoglossal trigone, preolivary sulcus, and 12th nerve root sleeve. Neurovascular contact was identified in 61% of root bundles. The roots were distorted in 44% of these contacts.

CONCLUSIONS

The contrast-enhanced 3D CISS sequence consistently displayed the cisternal segment as well as the canalicular segments of the hypoglossal nerve and is, therefore, the best sequence to visualize the complete cranial course of this nerve. Landmarks such as the 12th nerve sleeves can assist in the identification of this nerve.

Cranial nerve XII: the hypoglossal nerve

The hypoglossal nerve, cranial nerve XII, is the motor supply of the tongue. An understanding of the intracranial and extracranial components is fundamental in the evaluation of hypoglossal pathology. The following discussion of the evaluation of the hypoglossal nerve will involve the embryology, anatomy, clinical basis, and imaging techniques with pathologic correlations.

Cavernous malformation of the hypoglossal nerve: case report and review of the literature

OBJECTIVE

To describe a patient who presented with a hypoglossal nerve palsy caused by a cavernous malformation, review the literature on cavernous malformations associated with cranial nerves and the differential diagnosis of hypoglossal palsy.

RESULTS

Partial resection of the lesion was achieved and the diagnosis of cavernous malformation proven histologically.

CONCLUSIONS

Involvement of a cranial nerve by a cavernous malformation is very uncommon and the facial nerve is the example most frequently reported. This case report adds another possible site for this rare occurrence.

Microsurgical anatomy of the facial nerve trunk

Dissection and manipulation of the facial nerve (FN) trunk between its exit from the cranial base through the stylomastoid foramen (SMF) and its bifurcation is a critical step in various otologic, plastic and neurosurgical procedures. This study demonstrates the anatomical relationships and variability of the FN trunk with emphasis on some important morphometric data, particularly with relevance to hypoglossal-facial nerve anastomosis (HFA). Bilateral microsurgical dissection was performed on twenty-three human cadavers fixed with formalin. The whole trunk of the FN was exposed, its diameter at the SMF and its length were measured, its branches were observed and the site of its bifurcation was determined. Anastomotic connections with other nerves and blood supply of the trunk were studied. The FN invariably emerged from the cranial base through the SMF. Its diameter upon its emergence from the foramen was 2.66 +/- 0.55 mm. Two branches consistently originated from the trunk: the posterior auricular nerve and the nerve to the digastric muscle. Less consistent were the communicating branch with the glossopharyngeal nerve and the nerve to the stylohyoid muscle. The bifurcation of the FN occurred before its penetration into the parotid gland in 15% of cases and within the gland in 85%. The length of the FN trunk was 16.44 +/- 3.2 mm. Anastomoses between the FN and other nerves were observed in one-third of the dissections. The blood supply to the FN trunk was provided by the stylomastoid artery that was identified in 91% of cases. Understanding the microsurgical anatomy of the FN trunk is essential for performing any surgical procedure in the relevant region. Surgical implications of this study are presented with emphasis on HFA surgery.

b-series Ganglioside deficiency exhibits no definite changes in the neurogenesis and the sensitivity to Fas-mediated apoptosis but impairs regeneration of the lesioned hypoglossal nerve

The polymorphic carbohydrate structures of gangliosides play regulatory roles. In particular, b-series gangliosides, all of which contain alpha-2,8 sialic acids, have been considered to be critical in various biological events such as adhesion, toxin binding, neurite extension, cell growth, and apoptosis. To clarify the physiological functions of b-series gangliosides in vivo, we have established a gene knockout mouse of GD3 synthase. Although all b-series structures were deleted in the mutant mice, they showed an almost complete nervous tissue morphology with no apparent abnormal behavior. Moreover, no differences in Fas-mediated apoptotic reaction of lymphocytes between wild type and the mutant mice were detected. However, the mutant mice exhibited clearly reduced regeneration of axotomized hypoglossal nerves compared with the wild type, suggesting that b-series gangliosides are more important in the repair rather than in the differentiation of the nervous system and apoptotic process induced via Fas.