Usefulness of trigeminal somatosensory evoked potentials to detect subclinical trigeminal impairment in multiple sclerosis patients

Trigeminal somatosensory evoked potentials (TSEPs) by surface electric pulse stimulation were recorded in 30 normal subjects and in 70 multiple sclerosis (MS) patients, 13 of whom presenting clinical trigeminal impairment. We observed significant prolongation of all TSEPs parameters in MS group. TSEPs were abnormal in 45 patients (64.3%). Clinical and neurophysiological data agreed in 36 patients (51%) on 84 sides (60%). TSEPs were able to detect clinically silent lesions 54 times. TSEPs recording proves to be an additional useful test in MS multimodal evoked potential protocols.     

Recovery of nerve conduction following microvascular decompression for trigeminal neuralgia

OBJECTIVE: To assess the function of trigeminal nerve before and after microvascular decompression for trigeminal neuralgia. BACKGROUND: To date there is no direct evidence that microvascular decompression of the trigeminal root restores normal conduction in the nerve. METHODS: The authors examined 10 patients with trigeminal neuralgia in whom preoperative MRI and MR angiography demonstrated neurovascular contact. During microvascular decompression, the trigeminal nerve was monitored by recording early scalp trigeminal evoked potentials immediately before, during, and after decompression. Direct recordings from the root entry zone were also performed. RESULTS: In all patients preoperative scalp evoked potentials showed impaired conduction of the trigeminal root. Microvascular decompression was associated with immediate recovery of conduction in seven patients, demonstrated by both scalp evoked potentials and direct root recordings. All 10 patients were pain free postoperatively. CONCLUSIONS: Improvement in trigeminal neuralgia following microvascular decompression is often associated with normalization of neurophysiologic data, suggesting recovery of nerve function. Rapid electrophysiologic recovery and pain relief following microvascular decompression argue that neither phenomenon is linked to remyelination. It is possible that the trigeminal evoked potentials might predict an effective microvascular decompression.     

Nevus of Ota acquisita of late onset

Nevus of Ota is a melanotic pigmentary disorder characterized by its distinctive cutaneous distribution involving skin innervated by the trigeminal nerve. Most cases are clinically manifest at birth or around puberty; however, acquired lesions in adults have been reported. We report a case of nevus of Ota acquisita that occurred in an eighty-one-year-old man.     

Spinal trigeminal tractotomy and nociceptive reactions evoked by tooth pulp stimulation in the cat

The effect of transection of the descending root of the spinal trigeminal tract on nociceptive and aversive reactions evoked by stimulation of the tooth pulp nerve was studied in cats. The transection was performed 1-1.5 mm caudally to the obex. 1. The nociceptive reaction, characterized by wide opening of the jaw, dorsiflexion and rotation of the head and by signs of affective behaviour, remained unchanged after transection of the descending root of the trigeminal nerve (n = 6). 2. The instrumental escape reaction was elaborated in three cats before transection of the descending root of the trigeminal nerve and in three cats after transection. The escape reaction was retained after transection of the descending root and the speed of learning to escape the tooth pulp stimulation did not significantly differ in these two groups of animals. 3. It is to be concluded that the transection of the descending root of the spinal trigeminal tract in the cat does not result in dental analgesia.     

A case of rapidly progressive T cell type malignant lymphoma which started with multiple cranial neuropathy

A 35-year-old man had suffered from recurrent right trigeminal nerve palsy and flaccid paraparesis for about five months. Cerebrospinal fluid (CSF) showed a marked increase of protein (400 mg/dl) and mononuclear cells (146/mm3), but there were no malignant cells. Antibiotic therapy remitted his inguinal and mediastinal lymph nodes swelling, and trigeminal nerve palsy had recovered spontaneously. Then he developed left trigeminal and facial nerve palsy, mononeuropathy multiplex, and cauda equina syndrome. Nerve conduction studies revealed delayed velocity and reduction of amplitude. Enhanced magnetic resonance imaging showed increased signal intensity in bilateral trigeminal nerves, left internal auditory meatus, and meninges of the basal cistern. Also, there were two mass lesions in cauda equina. They were operated by orthopedist, and were not malignant. After that, CSF cells of malignant lymphoma were elevated and revealed T cell type (large cell). Then the patient exacerbated in bulbar palsy and died. When there is lymph node swelling with multiple neurological deficits, despite remission of lesions and signs, biopsies should be positively pursued early in the patient's clinical course.     

A performance comparison of communication links between rural hospitals and a digital health sciences library

CO2 laser pulses selectively excite A-delta and C mechano-thermal nociceptors in the superficial layers of the skin. To study the jaw-opening reflex elicited by a purely nociceptive input, we delivered laser pulses to the perioral region in 15 subjects. Sensory threshold was very low (9 mJ/mm2). High-intensity noxious laser pulses (more than 4 x sensory threshold) evoked a single phase of electromyogram suppression (laser silent period, LSP) at an onset latency of 70 ms in the contracted masseter and temporal muscles, bilaterally. Even maximum-intensity laser pulses failed to activate the suprahyoid muscles. The recovery curves to paired laser stimuli showed that at short interstimulus intervals the test LSP was strongly suppressed. At about 380 ms it recovered to 50%, i.e. its recovery curve resembled that of the masseter late silent period after electrical mental nerve stimulation (SP2). In experiments studying the interaction with heterotopic stimuli and non-nociceptive responses, chin-taps or electrical shocks delivered to the supraorbital, infraorbital or mental nerves before laser stimulation strongly suppressed the LSP. A preceding perioral laser pulse strongly suppressed the masseter SP evoked by supraorbital stimulation and the SP2 evoked by mental stimulation, but left SPI unaffected. We conclude that the perioral A-delta fibre input elicits a jaw-opening reflex simply by inhibiting the jaw-closers. The LSP response is mediated by a multisynaptic chain of brainstem interneurons and shares with the masseter SP2 part of the central circuit in the ponto-medullary region. We also propose that a common centre processes the various inputs for jaw opening.     

Facilitation of somatosensory evoked potentials by exploratory finger movements

Modification of somatosensory processing depending on the behavioral setting was studied. Active alternating movements of the fingers, passive tactile stimuli to the hand, and active exploration of objects were performed during recording of somatosensory evoked potentials (SEPs). SEPs were elicited by compound electrical median nerve stimulation and electrical stimulation at detection threshold of cutaneous median nerve fascicles identified by microneurography. Electrical stimulation was not time-locked to the studied condition. In comparison with SEPs at rest there was attenuation of early cortical potentials up to 25 ms post-trigger in all nonresting conditions. In stimulation of the compound median nerve as well as of isolated cutaneous fascicles of a hand actively exploring an object there was an additional increased negativity, peaking at 28 ms. This facilitory effect was independent of attentional focusing and was absent during exploration using the ipsilateral, non-electrically stimulated hand. In patients with parietal lesions the facilitatory effect was diminished on the affected side. Spline interpolated brain maps at this latency based on 32-channel recordings in healthy volunteers showed a shift of local contralateral positive maximum from frontal to parietal during exploration, indicating enhancement of a tangential dipole. It is suggested that in conditions involving close sensorimotor interaction such as exploratory hand movements there is preactivation of a cortical area which is located in the central sulcus and receives cutaneous somatosensory inputs.     

Functional connectivity in the rodent trigeminal pathway grown in vitro

In explant cocultures of the rat trigeminal pathway, embryonic trigeminal ganglion cells grow their axons into peripheral cutaneous and central nervous system targets (R.S. Erzurumlu, S. Jhaveri, Target influences on the morphology of trigeminal axons, Exp. Neurol, 135 (1995) 1-16; R.S. Erzurumlu, S. Jhaveri, H. Takahashi, R.D.G. McKay, Target-derived influences on axon growth modes in explant cocultures of trigeminal neurons, Proc. Natl. Acad. Sci. USA 90 (1993) 7235-7239). In heterochronic cocultures, composed of embryonic trigeminal ganglion, embryonic whisker pad and postnatal brainstem slice, trigeminal axons develop arbors and terminal boutons in the brainstem trigeminal nuclei. To determine whether these terminal arbors establish functional connections with the brainstem neurons, we examined the electrophysiological properties of brainstem neurons and their responsiveness to trigeminal ganglion stimulation. Intracellular recordings were done in vitro on cells of the trigeminal subnucleus interpolaris (SPI) in trigeminal pathway cocultures (E15 whisker pad, E15 trigeminal ganglion, and postnatal day (PND) 0-2 brainstem slice) or in the SPI of acutely prepared brainstem slices. Electrophysiological properties of SPI cells in both preparations were virtually identical. The voltage responses of SPI neurons to intracellular current injection were highly linear suggesting they lacked a number of voltage-dependent conductances. Depolarizing current injection produced trains of action potentials with a frequency that varied with stimulus intensity. In explant cocultures, electrical activation of the trigeminal ganglion evoked EPSPs, and EPSPs coupled with IPSPs in SPI cells. Bicuculline blockade of IPSP activity resulted in long lasting EPSPs whose duration increased with membrane depolarization. These results show that brainstem trigeminal neurons can retain their functional properties in culture and establish functional connections with primary sensory afferents.     

Effects of neuropeptide Y on intrarenal hemodynamics, plasma renin activity and urinary sodium excretion in rats

The cortical silent period evoked by magnetic transcranial stimulation and the peripheral silent period were studied in healthy subjects after intravenous injection of diazepam, baclofen or thiopental. None of the drugs tested changed the peripheral silent period. But, unexpectedly, diazepam significantly shortened the cortical silent period, the inhibitory effect lasting about 30 min. In experiments using paired transcranial stimuli, the conditioning shock inhibited the test response to a similar extent with and without diazepam. Although baclofen did not change the cortical silent period, it reduced the size of the H reflex in the forearm muscles. Thiopental also left the duration of the cortical silent period unchanged. These findings show that the cortical silent period can be modified pharmacologically. Diazepam possibly shortens the silent period by modulating GABA A receptors at a subcortical site.     

The distribution of afferent neurons in the trigeminal mesencephalic nucleus and the central projection of afferent fibers of the mylohyoid nerve in the rat

Horseradish peroxidase conjugated to wheatgerm agglutinin (HRP:WGA) was injected into the proximal cut ends of three branches of the mylohyoid nerve in rats: the branch to the mylohyoid muscle (BrMh), the branch to the anterior belly of the digastricus muscle (BrDg), and the cutaneous branch (BrCu). HRP-labeled cells were detected in the ipsilateral caudal portion of the trigeminal mesencephalic nucleus (Vmes) and the ipsilateral ventromedial division of the trigeminal motor nucleus, except when HRP:WGA was applied to the BrCu. Morphologically, all labeled Vmes cells were of the pseudounipolar type. Projections of the primary afferents of the BrMh were observed in the ipsilateral trigeminal nucleus caudalis, the upper cervical dorsal horns of laminae I-III, and the dorsolateral recticular formation (Rf), whereas the primary afferents of the BrDg terminated in the ipsilateral trigeminal nucleus principalis and Rf. These observations suggest that the role of the afferent inputs of the mylohyoid muscle differs from that of those of the anterior belly of the digastricus muscle in terms of several functions associated with jaw-closing and infrahyoid muscles.     

A phylogenetic assessment of the eukaryotic light-harvesting antenna proteins, with implications for plastid evolution

Stimulation of cutaneous foot afferents has been shown to evoke a facilitation of the tibialis anterior (TA) EMG-activity at a latency of 70-95 ms in the early and middle swing phase of human walking. The present study investigated the underlying mechanism for this facilitation. In those subjects in whom it was possible to elicit a reflex during tonic dorsiflexion while seated (6 out of 17 tested), the facilitation in the TA EMG evoked by stimulation of the sural nerve (3 shocks, 3-ms interval, 2.0-2.5x perception threshold) was found to have the same latency in the swing phase of walking. The facilitation observed during tonic dorsiflexion has been suggested to be -- at least partly -- mediated by a transcortical pathway. To investigate whether a similar mechanism contributes to the facilitation observed during walking, magnetic stimulation of the motor cortex (1.2x motor threshold) was applied in the early swing phase at different intervals in relation to the cutaneous stimulation in 17 subjects. In 13 of the subjects, the motor potentials evoked by the magnetic stimulation (MEPs) were more facilitated by prior sural-nerve stimulation (conditioning-test intervals of 50-80 ms) than the algebraic sum of the control MEP and the cutaneous facilitation in the EMG when evoked separately. In four of these subjects, a tibialis anterior H-reflex could also be evoked during walking. In none of the subjects was an increase of the H-reflex similar to that for the MEP observed. In five experiments on four subjects, MEPs evoked by magnetic and electrical cortical stimulation were compared. In four of these experiments, only the magnetically induced MEPs were facilitated by prior stimulation of the sural nerve. We suggest that a transcortical pathway may also contribute to late cutaneous reflexes during walking.     

Isolated cranial nerve palsies in multiple sclerosis

During a 10 year period 24 patients with definite multiple sclerosis with isolated cranial nerve palsies were studied (third and fourth nerve: one patient each, sixth nerve: 12 patients, seventh nerve: three patients, eighth nerve: seven patients), in whom cranial nerve palsies were the presenting sign in 14 and the only clinical sign of an exacerbation in 10 patients. MRI was carried out in 20 patients and substantiated corresponding brainstem lesions in seven patients (third nerve: one patient, sixth nerve: four patients, eighth nerve: two patients). Additional abnormal findings of electro-oculography, or masseter reflex, or blink reflex, or combinations of these were found in 20 patients and interpreted in favour of a brainstem lesion at the level of the respective cranial nerve. In 11 of 14 patients with isolated cranial nerve palsies as the presenting sign of multiple sclerosis, dissemination in space was documented by MRI, and in the remaining three by evoked potentials. In patients with multiple sclerosis with isolated cranial nerve palsies, MRI is the most sensitive method of documenting dissemination in space and electrophysiological testing the most sensitive at disclosing brainstem lesions.     

Activity staining of protein inhibitors of proteases on gelatin-containing polyacrylamide gel electrophoresis

Stimulation of the supraorbital branch of the trigeminal nerve (SO) elicited eye blinks in the rabbit, but did not decrease the amplitude of visual cortical evoked potential from stimulation of the optic chiasm (OX). In addition, the SO stimulation neither induced an inhibitory postsynaptic potential (IPSP) in LGN cells, nor activated inhibitory interneurons in the thalamic reticular nucleus (TRN), which proved to mediate both recurrent inhibition and saccadic suppression in the dorsal lateral geniculate nucleus (LGN). All these indicate that there is no visual suppression in the rabbit LGN during blink reflex.     

Enteropathogenic E. coli: intimacy redefined

A 42 yr old male presented with left facial weakness. MRI showed lesions affecting the distal seventh nerve and third division of the trigeminal nerve. The seventh nerve was biopsied and showed a malignant epithelioid schwannoma. The patient underwent extensive resection followed by irradiation. This is one of very few examples of intracranial malignant peripheral nerve sheath tumors and the first reported example of an intracranial malignant epithelioid schwannoma. The literature is reviewed and completeness of resection appears to be the most pertinent prognostic factor.     

Inhibition of trigeminal neurons by intravenous administration of the serotonin (5HT)1B/D receptor agonist zolmitriptan (311C90): are brain stem sites therapeutic target in migraine?

Migraine is a common and debilitating condition. Its treatment has received considerable attention in recent times with the introduction into clinical use of the serotonin (5HT)1B/D-like agonist sumatriptan. It is known from human studies that the intracranial blood vessels and dura mater are important pain-sensitive structures since mechanical or electrical stimulation of these vessels, such as the superior sagittal sinus, causes pain. We have developed a model of craniovascular pain by stimulating the superior sagittal sinus and monitoring trigeminal neuronal activity using electrophysiological techniques. In this study we determined the effect of intravenous administration of the novel anti-migraine compound zolmitriptan (311C90) upon evoked neuronal activity in trigeminal neurons. Nine adult cats were anaesthetised with alpha-chloralose (60 mg/kg, i.p.; 20 mg/kg, i.v., 2-hourly) with all surgery being conducted under halothane (1-3%). The superior sagittal sinus was isolated for electrical stimulation. Recordings were made from caudal trigeminal neurons at the C2 level of the cervical spinal cord with tungsten-in-glass microelectrodes. Signals were amplified and analysed by a custom-written program that enabled software filtering and extraction of both evoked potential and single cell data. Data were collected before and after administration of zolmitriptan. Electrical stimulation of the superior sagittal sinus resulted in activation of neuronal elements within the trigeminal nucleus that could be monitored as single unit activity or as evoked potentials, the latter reflecting both primary afferent and trigeminal cell body activity. The evoked potential recorded from the trigeminal nucleus was 207 +/- 14 microV and was reduced by zolmitriptan (100 micrograms/kg, i.v.) to a mean of 98 +/- 17 microV. Similarly, the probability of firing for trigeminal neurons was reduced from a control level of 0.63 +/- 0.1 to 0.13 +/- 0.05 after a dose of 100 micrograms/kg intravenously. These effects were dose-dependent and were significantly different from the effect of vehicle (P < 0.05). These data demonstrate that systemically administered zolmitriptan can inhibit evoked trigeminovascular activity within the trigeminal nucleus. This inhibition of trigeminal activity may play a role in the anti-migraine actions of this compound and offers the prospect of a third pathophysiologically consistent target site for anti-migraine drug effects.     

The characteristics of a natural attenuated isolate of Francisella tularensis

Multimodal evoked potentials in patients with trigeminal neuralgia are analyzed in the paper. The comprehensive studies of cortical trigeminal somatosensory evoked potentials, visual evoked potentials, and brainstem auditory evoked potentials have revealed their changes that are indicative of the impaired central mechanisms of afferentation in patients with trigeminal abnormality. The findings are discussed in the light of the theory of generator mechanisms of neuropathological pain syndromes.     

Computerized dynamic visual acuity test in the assessment of vestibular deficits

Hypoglossal facial anastomosis (HFA) is a standard surgical technique for restoration of facial movements in cases of intratemporal lesions of the facial nerve. Case reports provide evidence that an affected trigeminal system reduces functional outcome. In order to detect morphological changes in the hypoglossal nucleus responsible for this phenomenon, we used 18 Wistar rats and performed three different surgical combinations. In group 1, six animals received HFA only. In group 2, HFA was combined with resection of the contralateral infraorbital nerve. In group 3, HFA was combined with resection of the ipsilateral infraorbital nerve. Fifty-six days after the operation, horseradish peroxidase (HRP) was injected into the whisker pad. As shown in previous studies using HRP, retrograde-labelled motoneurons occurred in the hypoglossal and facial nuclei. Counts of the labelled motoneurons showed no change in the number of projecting hypoglossal motoneurons in group 2 when compared to HFA only, but a significantly smaller number in group 3 (-35%). Furthermore, the number of projecting facial motoneurons was significantly reduced in group 2 (-85%) and group 3 (-45%). These morphological findings indicate an absent or insufficient functional connection between the contralateral infraorbital nerve and the hypoglossal nucleus, and a strong influence of the infraorbital nerve to the ipsi- and contralateral facial nuclei. Additionally, our study provides morphological evidence that the integrity of the sensory trigeminal system is very important in reconstructive facial nerve surgery.     

The effect of peripheral glycerol on trigeminal neuropathic pain examined by quantitative assessment of abnormal pain and sensory perception

In nine patients with trigeminal neuropathic pain after nerve injury, we examined prospectively the effect of peripheral glycerol neurolysis on abnormal pain and sensory perception. In the painful facial skin area of these patients, we found increased temperature and tactile thresholds and the presence of abnormal temporal summation of pain. In seven patients, neuropathic pain was peripheral and disappeared after application of local anaesthesia at or proximal to the site of nerve injury. Neuropathic pain was central in two patients, and unresponsive to local anaesthesia applied proximal to the site of nerve injury. Six weeks after injection of glycerol proximal to the site of nerve injury, no or marginal pain relief was found in 8 patients with peripheral or central trigeminal neuropathic pain. On the other hand, in one of the patients with peripheral trigeminal neuropathic pain, glycerol was given at the site of nerve injury, and produced total pain relief for the whole observation period of 7 months. In this patient, pain relief was associated with normalisation of abnormal temporal summation of pain, which was not observed in the 8 patients with no or marginal pain relief. No further changes in temperature or tactile thresholds were found in any of the 9 patients after a single injection of absolute glycerol. Total pain relief in one of the patients probably is related to the ability of glycerol to inhibit ongoing ectopic impulse generation at the site of nerve injury. We suggest that glycerol-induced reduction of primary afferent hyperactivity may secondarily result in down-regulation of central neuronal hyperexcitability. The efficacy of application of glycerol at the site of nerve injury in patients with peripheral trigeminal neuropathic pain may warrant further investigation. However, this prospective study does not provide evidence that application of glycerol proximal to the site of nerve injury has a place in the treatment of trigeminal neuropathic pain.     

Inputs to trigeminal brain stem neurones from facial, oral, tooth pulp and pharyngolaryngeal tissues: I. Responses to innocuous and noxious stimuli

Responses evoked in anaesthetized or decerebrate cats by stimulation of afferents supplying the face, mouth, pharynx, larynx, tooth pulp and jaw muscles were recorded from single neurones located in the trigeminal (V) main sensory nucleus, V nucleus oralis, and adjacent regions. Many cells (both V-thalamic relay and non-relay with localized V mechanoreceptive cutaneous fields could be activated by stimulation of a number of these afferents. A particularly prominent short-latency (often monosynaptic) input was noted from the canine tooth pulp, stimulation of which is generally considered to elicit only responses of pain in man. Control experiments showed that pulp-evoked responses were not the result of stimulus spread to tissues outside the pulp. The interaction of these various inputs to neurones at this level of the V brain stem complex typically resulted in a prolonged period of inhibition that was sometimes preceded by a short-lasting facilitatory phase. This inhibitory effect was also apparent in neurones located outside the complex, although a late facilitatory phase was frequently also noted. Our findings indicate a significant nociceptive input to V main sensory-oralis neurones, a proportion of which relay directly to the ventrobasal thalamus. The interactions described may be involved in perceptual and reflex aspects of responses to noxious and innocuous V stimuli.