Mustard oils and cannabinoids excite sensory nerve fibres through the TRP channel ANKTM1

Wasabi, horseradish and mustard owe their pungency to isothiocyanate compounds. Topical application of mustard oil (allyl isothiocyanate) to the skin activates underlying sensory nerve endings, thereby producing pain, inflammation and robust hypersensitivity to thermal and mechanical stimuli. Despite their widespread use in both the kitchen and the laboratory, the molecular mechanism through which isothiocyanates mediate their effects remains unknown. Here we show that mustard oil depolarizes a subpopulation of primary sensory neurons that are also activated by capsaicin, the pungent ingredient in chilli peppers, and by Delta(9)-tetrahydrocannabinol (THC), the psychoactive component of marijuana. Both allyl isothiocyanate and THC mediate their excitatory effects by activating ANKTM1, a member of the TRP ion channel family recently implicated in the detection of noxious cold. These findings identify a cellular and molecular target for the pungent action of mustard oils and support an emerging role for TRP channels as ionotropic cannabinoid receptors.

Immediate-early regulatory gene mutants define different stages in the establishment and reactivation of herpes simplex virus latency

Using nonsense and deletion mutants of herpes simplex virus type 1, we investigated the roles of three immediate-early proteins (ICP4, ICP27 and ICP0) in the establishment and reactivation of ganglionic latency in a mouse ocular model. DNA hybridization, superinfection-rescue, and cocultivation techniques provided quantitative data that distinguished between the failure of a virus to establish latency in the ganglion and its failure to reactivate. Null mutants with lesions in the genes for ICP4 and ICP27 did not replicate in the eye or in ganglia and failed to establish reactivatable latent infections. Three ICP0 deletion mutants which could replicate in the eye and ganglia varied in their ability to establish and reactivate from the latent state, demonstrating that ICP0 plays a role both in the establishment and the reactivation of latency. The use of viral mutants and a variety of stage-specific assays allowed us to better define the stages in the establishment and reactivation of herpes simplex virus type 1 latency.

Metastasis to the base of the skull: clinical findings in 43 patients

We studied 43 patients with metastases to the base of the skull to determine whether clinical symptoms localized the lesions accurately. We identified five clinical syndromes: orbital, parasellar, middle fossa, jugular foramen, and occipital condyle. The orbital and parasellar syndromes were characterized by frontal headache, diplopia, and first-division trigeminal sensory loss. Proptosis occurred with the orbital but not the parasellar syndrome. The middle-fossa syndrome was characterized by facial pain or numbness. The jugular foramen syndrome was characterized by hoarseness and dysphagia, with paralysis of the ninth through eleventh cranial nerves. The occipital condyle syndrome was characterized by unilateral occipital pain and unilateral tongue paralysis.

Trigeminal primary afferent projections to "non-trigeminal" areas of the rat central nervous system

The central projections of rat trigeminal primary afferent neurons to various "non-trigeminal" areas of the central nervous system were examined by labeling the fibers with wheat germ agglutinin-horseradish peroxidase (WGA-HRP) transported anterogradely from the trigeminal ganglion. This technique produced a clear and comprehensive picture of trigeminal primary afferent connectivity that was in many ways superior to that which may be obtained by using degeneration, autoradiography, cobalt labeling, or HRP transganglionic transport techniques. Strong terminal labeling was observed in all four rostrocaudal subdivisions of the trigeminal brainstem nuclear complex, as well as in the dorsal horn of the cervical spinal cord bilaterally, numerous brainstem nuclei, and in the cerebellum. Labeling in the ipsilateral dorsal horn of the cervical spinal cord was very dense at C1, moderately dense at C2 and C3, and sparse at C4-C7. Numerous fibers crossed the midline in the medulla and upper cervical spinal cord and terminated in the contralateral pars caudalis and dorsal horn of the spinal cord from C1-C5. The latter axons terminated most heavily in the mandibular and ophthalmic regions of the contralateral side. Extremely dense terminal labeling was observed in the ipsilateral paratrigeminal nucleus and the nucleus of the solitary tract, moderate labeling was seen in the supratrigeminal nucleus and in the dorsal reticular formation, and small numbers of fibers were observed in the cuneate, trigeminal motor, lateral and superior vestibular nuclei, and in the cerebellum. The latter fibers entered the cerebellum in the superior cerebellar peduncle and projected to the posterior and anterior lobes as well as to the interposed and lateral deep cerebellar nuclei. Most projections in this study originated from fibers in the dorsal part of the spinal tract of V, suggesting a predominantly mandibular origin for these fibers. Projections from the ophthalmic and maxillary divisions, in contrast, were directed mainly to the cervical spinal cord bilaterally, to contralateral pars caudalis, and to certain areas of the reticular formation. In conclusion, this study has demonstrated that somatosensory information from the head and face may be transmitted directly to widespread and functionally heterogeneous areas of the rat central nervous system, including the spinal cord dorsal horn, numerous brainstem nuclei, and the cerebellum.(ABSTRACT TRUNCATED AT 400 WORDS)

Wrch-1, a novel member of the Rho gene family that is regulated by Wnt-1

We report the isolation and cloning of the Wrch-1 (Wnt-1 responsive Cdc42 homolog) cDNA. Wrch-1 is a novel gene whose mRNA level increases in response to Wnt-1 signaling in Wnt-1 transformed cells, Wnt-1 transgene induced mouse mammary tumors, and Wnt-1 retrovirus infected cells. Wrch-1 encodes a homolog of the Rho family of GTPases. It shares 57% amino acid sequence identity with Cdc42, but possesses a unique N-terminal domain that contains several putative PXXP SH3-binding motifs. Like Cdc42, Wrch-1 can activate PAK-1 and JNK-1, and induce filopodium formation and stress fiber dissolution. Active Wrch-1 stimulates quiescent cells to reenter the cell cycle. Moreover, overexpression of Wrch-1 phenocopies Wnt-1 in morphological transformation of mouse mammary epithelial cells. Taken together, Wrch-1 could mediate the effects of Wnt-1 signaling in the regulation of cell morphology, cytoskeletal organization, and cell proliferation.

A 20-year review of percutaneous balloon compression of the trigeminal ganglion

OBJECT

The aim of this study was to investigate outcomes and complication rates associated with percutaneous balloon compression (PBC) of the trigeminal ganglion over a long follow-up period.

METHODS

This retrospective review was conducted in 496 patients with typical symptoms of unilateral trigeminal neuralgia who underwent 531 PBCs of the trigeminal ganglion between 1980 and 1999. The mean length of follow up was 10.7 years. The treatment used was a modification of that first described by Mullan and Lichtor in 1983. There were nine technical failures. Of the 522 successful procedures, prompt pain relief ensued in all patients except one. Recurrence of pain was found in 95 patients (19.2%) within 5 years and in 158 patients (31.9%) over the entire study period. Symptomatic dysesthesias occurred in 19 patients (3.8%), but corneal anesthesia and anesthesia dolorosa did not.

CONCLUSIONS

In this review the authors present data on the largest cohort of patients with the longest follow up for this procedure in the current literature. The balance between the recurrence rate and troublesome sensory complications achieved in this series is favorable when compared with previously published studies on outcomes of PBC and the two alternative percutaneous methods, radiofrequency thermocoagulation and glycerol rhizolysis. The PBC procedure has additional advantages in that it is relatively straightforward and quick, and can be performed during a brief period of general anesthesia with no discomfort to the patient. This makes it an attractive first choice in the treatment of trigeminal neuralgia.

Acute and latent infection of sensory ganglia with herpes simplex virus: immune control and virus reactivation

The role of antiviral antibody in controlling the acute and latent phases of herpes simplex virus (HSV) infection in sensory ganglia of mice was studied in vitro and in vivo. Organ cultures of ganglia inoculated in vitro with HSV produced infectious virus for at least 3 weeks. In the presence of antiviral antibody, the titre of virus was markedly reduced, but the infection was not eliminated. Similarly, passive administration of antibody to HSV-infected immunodeficient (nude) mice reduced the virus titre but did not eliminate the acute phase of the ganglionic infection. Suppression of the cell-mediated immune response in latently infected immunocompetent mice by treatment with cyclophosphamide and/or X-irradiation resulted in reactivation of HSV in up to 70% of the animals. Reactivation was demonstrated by recovering infectious virus in cell-free homogenates of ganglia and eye globes and by finding virus antigens in ganglia by immunofluorescent staining. Reactivation occurred both in vitro and in vivo in the presence of high concentrations of neutralizing antibody. It is concluded that antibody alone is not sufficient to eliminate the acute phase of the ganglionic infection and that cytotoxic agents known to suppress the host's cellular immune response can reactivate virus in the presence of neutralizing antibody.

Percutaneous retrogasserian glycerol rhizotomy. Predictors of success and failure in treatment of trigeminal neuralgia

Eighty-five medically intractable trigeminal neuralgia patients treated by percutaneous retrogasserian glycerol rhizotomy (PRGR) were followed for 6 to 54 months. The median time to recurrence of symptoms refractory to medical therapy and requiring further intervention was 3 years (by Kaplan-Meier survival analysis). The median time to recurrence of symptoms requiring some form of medical treatment was 2 years. Following repeat PRGR for recurrent symptoms, the median time to recurrence was 1 year. Univariate log rank statistics and multivariate Cox proportional hazards modeling revealed significant associations between favorable outcome and female sex, absence of atypical features or associated cluster headache symptoms, success of prior carbamazepine therapy, duration of symptoms, and cerebrospinal fluid return during the procedure. A scoring system using prognostic factors has been developed based upon these findings. Assessment of published studies of PRGR and of other treatments for trigeminal neuralgia is made difficult by the variety of outcome measures employed and variable follow-up intervals. The present study attempts to address these issues by definition of endpoints, statistical analysis of the data, and identification of important prognostic factors in a manner useful to the clinician.

Percutaneous retrogasserian glycerol injection in the management of trigeminal neuralgia: long-term follow-up results

The results in 122 patients with trigeminal neuralgia who underwent percutaneous retrogasserian glycerol injection are presented. Eighty patients were followed from 38 to 54 months. The recurrence rate at 54 months was 72% (Kaplan-Meier analysis), and the median pain-free interval was 32 months. Complications associated with the procedure were significantly high: 63% of the patients had definite hypesthesia of the face and 29% had unpleasant dysesthesias, including two cases of anesthesia dolorosa. Sensory disturbances were most frequent in patients who had received a previous alcohol block procedure. Among the patients without previous peripheral procedures, 50% developed sensory disturbances. Because of the high rates of recurrence and sensory disturbances, the authors prefer microvascular decompression for the management of trigeminal neuralgia.

Reterogasserian anhydrous glycerol injection therapy in trigeminal neuralgia: observations in 552 patients

Five hundred and fifty two patients with trigeminal neuralgia were treated with reterogasserian anhydrous glycerol injections. Two hundred and twenty four patients (59.1%) at the end of two years and eight patients (8.1%) at the end of six years were free from pain after a single injection. There was recurrence of pain in 136 patients (27.7%) after one year and in an additional 155 patients (40.9%) after two years. The recurrence was seen earlier in patients who had either a neurolytic injection or had undergone surgical procedures, compared with those patients who had been treated with drugs. Complications of injection were few and not incapacitating. The technique was found to be safe, cheap and effective in treating trigeminal neuralgia, and is recommended for centres where there are financial constraints.

Peripheral and gasserian ganglion-level procedures for the treatment of trigeminal neuralgia

This review discusses the various peripheral and ganglion-level procedures available for treating trigeminal neuralgia and summarizes specific success and complication rates for each technique.

METHOD

A review of the available literature.

RESULTS

It appears that expertly performed ganglion-level procedures (radiofrequency thermocoagulation, balloon compression, and glycerolysis) are more effective than peripheral procedures but neither approach can be relied on to produce long-term pain relief. All of these procedures are neurodestructive and can cause sensory loss and dysesthesia. Effective drug therapy may not be acceptable to some patients as adverse cognitive side effects are increasingly recognized.

CONCLUSIONS

Each patient should receive an informed and impartial account of the available surgical options. There is a need for prospective randomized controlled studies in procedure-naïve subjects to determine the optimal surgical management of trigeminal neuralgia.

Treatment of trigeminal neuralgia and other facial pains by retrogasserian injection of glycerol

Håkanson's treatment of trigeminal neuralgia by injecting 0.2 to 0.4 ml of glycerol into the cerebrospinal fluid in Meckel's cave was carried out in 27 patients with trigeminal neuralgia, 3 with atypical facial neuralgia, and 1 with post-traumatic facial neuralgia. Minor modifications of his technique are described based on our finding of a greater pain and sensory loss upon injection than he noted. We present evidence that glycerol is more toxic than its cryoprotectant effect would intimate and that it selectively eliminates those components of the compound action potential in the trigeminal rootlets customarily associated with pain. We conclude that the method is probably going to be an improvement over radiofrequency heating for the treatment of trigeminal neuralgia in many situations.

Latent herpes simplex virus trigeminal ganglionic infection in mice and demyelination in the central nervous system

Mice were inoculated with herpes simplex virus (HSV) type 1 by gently scraping the skin of the nose with a fine needle. About 80% of the animals developed latent inapparent HSV infections in trigeminal ganglia. Virus was demonstrable for at least 6 months post inoculation (p.i.) by cocultivation of ganglionic tissue with GMK cells. Histologically, trigeminal ganglia revealed infiltrations of inflammatory cells even 6 months p.i. In addition, lesions occurred in the brainstem corresponding to the entry of trigeminal roots, trigeminal tracts and nuclei. Inflammatory cell infiltration, disruption of myelin sheaths and macrophages laden with myelin degradation products were observed 7 days p.i. Fourteen to 30 days p.i. electron microscopy demonstrated completely naked axons. In the transitional region of the trigeminal root denuded axons occurred in the central part of the region while the peripheral myelin, bordering the demyelinated central segments, was intact. Small areas of demyelination were still detectable 3 and 6 months p.i. but there were then also signs of remyelination. Possible mechanisms causing the demyelinations are discussed.

Percutaneous Retrogasserian Glycerol Rhizotomy in the Treatment of Tic Douloureux Associated with Multiple Sclerosis

OBJECTIVE:

Patients with multiple sclerosis (MS) have a relatively high incidence of tic douloureux (TD) and often do not tolerate medical therapy well. The minimally invasive nature of percutaneous retrogasserian glycerol rhizotomy (PRGR) renders it ideal for first-line surgical treatment of TD. We sought to ascertain the benefits of PRGR in patients with MS and to determine whether hypalgesia after PRGR correlates with efficacy.

METHODS:

We assessed 97 glycerol procedures performed in 53 patients followed prospectively for treatment of TD associated with MS. Factors assessed included degree of pain relief, postoperative hypalgesia, procedural morbidity, medication use, time to pain recurrence, and number and type of subsequent procedures.

RESULTS:

Complete pain relief was obtained in 78% of patients after the initial glycerol injection, and partial relief was obtained in 13% of patients. Long-term follow-up (mean, 81 mo) demonstrated a recurrence rate of 59%, with a mean time to recurrence of 17 months. Actuarial recurrence rates were 50% at 12 months and 60% at 24 months. Twenty-four patients underwent a second or subsequent PRGR for recurrent pain and achieved similar rates of pain relief and time to recurrence. Facial sensory loss was associated with a higher likelihood of pain relief (P < 0.05), with longer time to pain recurrence (P < 0.05), and with decreased use of medication after surgery (P < 0.01.)

CONCLUSION:

PRGR is an effective, low-morbidity surgical procedure in the management of TD complicating MS. The presence of facial sensory loss after PRGR is associated with prolonged efficacy.

NGF mRNA expression in developing cutaneous epithelium related to innervation density

To determine if the initial level of NGF mRNA in developing cutaneous epithelium is correlated with its final innervation density, we measured the concentration of NGF mRNA in the epithelia of the maxillary, mandibular and ophthalmic territories of trigeminal ganglion in the embryonic mouse. At the onset of neuronal death in the ganglion there were marked differences in the concentration of NGF mRNA in these epithelia: the level was highest in the epithelium of the densely innervated maxillary territory, it was lower in the epithelium of the moderately innervated mandibular territory and was lowest in the epithelium of the sparsely innervated ophthalmic territory. These regional differences in the level of NGF mRNA during the early stages of target field innervation suggest that the level of NGF production in target field cells, rather than regional differences in the access of innervating neurons to NGF, governs the number of neurons that survive. Because the same percentage cell death occurs in each of the subsets of trigeminal neurons that innervate the maxillary, mandibular and ophthalmic territories, regional differences in NGF synthesis are not responsible for establishing differences in innervation density, rather they maintain differences that arise earlier in development.

Analgesia by electrostimulation of the trigeminal ganglion in patients with trigeminopathic pain: a PET activation study

Electrostimulation of the trigeminal ganglion (TGES) has shown good results in treatment of trigeminopathic pain in selected patients. To map the mechanisms of TGES analgesia, we determined changes in relative regional cerebral blood flow (rCBF) in ten patients with trigeminopathic pain using positron emission tomography. The patients were scanned before stimulation (habitual pain), after short-term stimulation (1 min, stTGES) and after long-term stimulation (ltTGES). Highly significant pain alleviation was reported after ltTGES. Relative rCBF changes after stTGES, which was without significant pain relief, were attributed mainly to intrinsic TGES effects. A statistical comparison of the subtraction images of ltTGES and stTGES disclosed significant rCBF increases after ltTGES in rostral parts of anterior cingulate cortex (ACC) and neighboring orbitofrontal and medial frontal cortices. Regression analysis of rCBF changes and subjective ratings of pain revealed an inverse relationship in the ipsilateral rostral ACC, and only rCBF changes in the caudal part of the contralateral ACC were consistent with the encoding of pain. The present study provides evidence for a pain modulating role of the rostral ACC, critically important in electrostimulation-induced analgesia, and identifies the caudal ACC as a region encoding pain sensation.

Percutaneous trigeminal ganglion compression for trigeminal neuralgia. Experience in 22 patients and review of the literature

Between 1983 and 1988, a percutaneous trigeminal ganglion compression (PTGC) procedure for trigeminal neuralgia was performed on 22 patients. All patients were initially relieved of their pain. There were three recurrences (14%); two of these patients underwent a second PTGC procedure and one a partial trigeminal nerve root section. Follow-up examination 3 to 53 months after the procedure showed that all patients were free of pain. Morbidity included persistent minor hypesthesia in five patients, persistent minor dysesthesias in three, persistent minor weakness in three, aseptic meningitis in one, transient sixth nerve palsy in one, and transient otalgia in three. None of the patients had either anesthesia dolorosa or an absent corneal reflex.

Contributions from the upper cervical dorsal roots and trigeminal ganglia to the feline circle of Willis

To further define the sensory projections to the circle of Willis, we measured concentrations of immunoreactive substance P in pial arteries of cats following either bilateral removal of the C1-3 dorsal root ganglia (six cats) or bilateral removal of the trigeminal ganglia (three cats). Removal of the dorsal root ganglia decreased concentrations of the tachykinin substance P in the vertebral artery and the basilar artery and its branches by 72% and 50-66%, respectively. Bilateral removal of the trigeminal ganglia decreased substance P concentrations in all forebrain vessels including the rostral basilar artery, although only concentrations in the anterior cerebral artery were significantly lower than those in unilaterally lesioned cats (p less than 0.01). Hence, the vertebrobasilar artery and its tributaries are invested by substance P-containing fibers originating from the upper cervical dorsal root ganglia, and the anterior cerebral artery is innervated by both trigeminal ganglia. If a similar anatomy exists in humans, our data provide an explanation for the occipital localization of headaches arising from the vertebrobasilar arteries and for bilateral headaches following stimulation of the anterior cerebral artery.

Trigeminal schwannomas: results of Gamma Knife surgery in 37 cases

Object

Information on outcomes of Gamma Knife surgery (GKS) for patients harboring trigeminal schwannomas is limited because these tumors are rare. The authors evaluated tumor control and functional outcomes in patients who underwent GKS for trigeminal schwannomas to clarify the efficacy of this treatment.

Methods

Forty-two patients with trigeminal schwannomas but no evidence of neurofibromatosis Type 2 were treated with GKS at Komaki City Hospital between November 1991 and December 2003. Of these, 37 patients were assessed. The mean tumor volume in these patients was 10 cm3. The mean maximum radiation dose directed to the tumor was 27.9 Gy and the mean dose directed to the tumor margin was 14.2 Gy. The mean follow-up period was 54 months. In four patients (11%) there was complete tumor remission; in 20 (54%) there was partial tumor remission; in eight (22%) the disease remained stable; and in five (14%) the tumor enlarged or uncontrollable facial pain developed with radiation-induced edema requiring resection. The actuarial 5- and 10-year tumor control rates were both 84%. With respect to functional outcomes, 40% of patients noted an improvement in their symptoms, and one patient experienced new symptoms despite good tumor control.

Conclusions

Gamma Knife surgery was a safe and effective treatment for a select group of patients harboring trigeminal schwannomas. Large tumors that compress the brainstem and cause deviation of the fourth ventricle should first be removed surgically and any remnant should be treated by GKS.

Tissue culture of adult human neurons

Dissociated neurons from adult human trigeminal and superior cervical ganglia were cultured in vitro for more than 2 months. Immediately after dissociation by incubation in 0.06% collagenase for 15--18 h, the cultures consisted of single neurons or clumps of neurons and degenerating fragments of myelinated or non-myelinated axons. After 7--10 days, bipolar Schwann cells, large neurons and fine nerve fibers were observed. Electron microscopic examination of these neurons revealed all the ultrastructural features of healthy adult neurons including those of lipofuscin pigments. By electrophysiological technique, extracellular recording to action potentials generated by these neurons were obtained indicating the neurons were alive and healthy. The availability of adult human neurons in culture should provide a model system for investigation related to the pathomechanism of lipofuscin formation and aging in general.