Neurometabolite Levels and Relevance to Central Sensitization in Chronic Orofacial Pain Patients: A Magnetic Resonance Spectroscopy Study.

Background: Refractory chronic pain in the orofacial region involves central sensitization (CS). However, not all chronic pain patients exhibit CS. An objective assessment of CS may be useful for pain management. Changes in the balance of excitatory and inhibitory neural activity or excessive activity of nerves and glial cells may cause CS and contribute to pain chronification. Patients and Methods: 1H-magnetic resonance spectra were acquired from the anterior cingulate cortex (ACC) and thalamus in 20 patients with chronic orofacial pain and suspected CS, and 21 healthy volunteers, using a single-voxel point-resolved spectroscopy sequence. The patients were assessed using the Central Sensitization Inventory. Results: Aspartate/total creatine (tCr) and glutathione in the ACC were significantly higher in the patient group. However, no significant difference was observed between groups in the neurometabolites measured in the thalamus. Patients also exhibited a tendency for increased gamma-aminobutyric acid (GABA)/tCr in the ACC. There were positive relationships between Central Sensitization Inventory scores and glutamate + glutamine (Glx) in the thalamus, a positive trend for Glx in the ACC and a negative relationship for GABA/tCr in the ACC. Conclusion: The high levels of aspartate/tCr and glutathione in the patient group suggest excitatory neuronal activity and hyperactivity of neurons and glial cells. The correlation analysis results suggest that excitatory and inhibitory neurometabolites are involved in the chronification of orofacial pain, including CS.

Nasogastric Tube Knotted Around a Nasal Endotracheal Tube in the Nasopharynx: Possible Cause.

A nasogastric tube is often used along with a nasal endotracheal tube during oral surgery or dental treatment under general anesthesia. Although the insertion of a nasogastric tube is a simple procedure, it can be associated with complications that lead to potentially serious consequences. The knotting of a nasogastric tube around an endotracheal tube is rare. Here, we report a case in which the nasogastric tube became knotted around the nasal endotracheal tube in the nasopharynx. We compare this case with 4 previous similar cases and provide a theory of how the nasogastric tube might have become knotted.

Effect of the parasympathetic vasodilation on temperature regulation via trigeminal afferents in the orofacial area.

The skin temperature (Tm) of the orofacial area influences orofacial functions and is related to the blood flow (BF). Marked increases in BF mediated by parasympathetic vasodilation may be important for orofacial Tm regulation. Therefore, we examined the relationship between parasympathetic reflex vasodilation and orofacial Tm in anesthetized rats. Electrical stimulation of the central cut end of the lingual nerve (LN) elicited significant increases in BF and Tm in the lower lip. These increases were significantly reduced by hexamethonium, but not atropine. VIP agonist increased both BF and Tm in the lower lip. The activation of the superior cervical sympathetic trunk (CST) decreased BF and Tm in the lower lip; however, these decreases were significantly inhibited by LN stimulation. Our results suggest that parasympathetic vasodilation plays an important role in the maintaining the hemodynamics and Tm in the orofacial area, and that VIP may be involved in this response.

Retropharyngeal Dissection by Parker Flex-Tip Nasal Endotracheal Tube.

Possible complications of nasotracheal intubation include injury to the nasal or pharyngeal mucosa. Dissection of the retropharyngeal tissue by the endotracheal tube is one of the rarer of the more severe complications. Previous studies have indicated that the Parker Flex-Tip (PFT) tracheal tube (Parker Medical, Highlands Ranch, Colo) reduces the incidence of mucosal injury. We experienced a case involving inadvertent retropharyngeal placement of a PFT tube in a 29-year-old patient during nasotracheal intubation under general anesthesia for elective dental treatment. Despite thermosoftening the PFT tube, expanding the nasal meatus, and ensuring gentle maneuvering, the tube intruded into the left retropharyngeal mucosa. However, the injury was not severe, and the only required treatment was the administration of antibiotics and corticosteroids. Even when a PFT tube is utilized, pharyngeal dissection is possible. When resistance is felt during passing of the PFT tube through the nasopharynx, an alternative method to overcome this resistance should be utilized.

High-contrast high-resolution imaging of posttraumatic mandibular nerve by 3DAC-PROPELLER magnetic resonance imaging: correlation with the severity of sensory disturbance.

OBJECTIVE: Magnetic resonance neurography reveals abnormal morphologies of regenerated nerves and overgrown connective tissue in injured trigeminal nerves, suggesting neuroma formation. We hypothesized that such deformities and scar formation contribute to pain symptoms. STUDY DESIGN: High-contrast high-resolution magnetic resonance imaging was utilized to evaluate the inferior alveolar nerve and lingual nerve following traumatic injury in 19 patients. The relationship between the morphologic classification and severity of the sensory disorder was assessed. RESULTS: In all cases, 3-dimensional anisotropy contrast periodically rotated overlapping parallel lines with enhanced reconstruction (3DAC-PROPELLER) successfully revealed the inner structures within the lesion. The isolated type represented the normal course of the nerve isolated from scar-like tissue (8 cases), whereas the deformity type included the deformed nerve either within scar-like tissue or by itself, unassociated with surrounding scar-like tissue (9 cases). In the remaining 2 cases, the nerve tissue and scar-like tissue were incorporated. Patients with the deformity type exhibited significantly more severe pain symptoms compared with patients with the isolated type. CONCLUSIONS: Overgrown connective tissue does not necessarily block regenerating nerves and itself may not cause pain. The morphologic findings on the 3DAC-PROPELLER were relevant to the severity of pain symptoms.

Prognosis After Surgical Treatment of Trigeminal Neuropathy with a PGA-c Tube: Report of 10 Cases.

OBJECTIVE: Although surgery using a polyglycolic acid-collagen (PGA-c) tube is effective for peripheral nerve injury-induced chronic hand pain, it has not been applied to trigeminal nerve lesions because of the difficult approach. We used a PGA-c tube during surgery for trigeminal neuropathy and evaluated its prognosis based on the outcomes. DESIGN: Case report. SETTING AND PATIENTS: In the dental anesthesia division of a university hospital, 11 patients with severe dysesthesia underwent surgical repair of a damaged lingual nerve (LN) or inferior alveolar nerve (IAN). One patient was lost to follow-up. Changes in quantitative sensory testing (QST) and the presence of dysesthesia as a treatment outcome were compared preoperatively and postoperatively in 10 patients. Two surgical treatments, bridging or encircling peripheral nerves, were applied. Bridging of both stumps was selected when neurotmesis was detected or the nerve was lacerated during surgery (N = 4). Otherwise, a longitudinal PGA-c tube was used to encircle the lesion (N = 6). Outcomes were evaluated 2 months to 8 years postoperatively. RESULTS: Both methods improved the patients' condition based on QST results (brush stroke perception, mechanical touch threshold, sensitivity to cold/hot stimuli). Preoperative allodynia or dysesthesia was resolved in six patients and greatly reduced in four. Two patients (one with inflammation-induced pain, one with implant-related pain) developed prolonged postoperative allodynia requiring pain-relief medication. CONCLUSIONS: Use of a PGA-c tube for surgical treatment of intractable pain due to LN or IAN neuropathy helps alleviate sensory impairment. The possibility of new dysesthesias emerging postoperatively, however, should be noted.

Detectability of neural tracts and nuclei in the brainstem utilizing 3DAC-PROPELLER.

Despite clinical importance of identifying exact anatomical location of neural tracts and nuclei in the brainstem, no neuroimaging studies have validated the detectability of these structures. The aim of this study was to assess the detectability of the structures using three-dimensional anisotropy contrast-periodically rotated overlapping parallel lines with enhanced reconstruction (3DAC-PROPELLER) imaging. Forty healthy volunteers (21 males, 19 females; 19-53 years, average 23.4 years) participated in this study. 3DAC-PROPELLER axial images were obtained with a 3T-MR system at four levels of the brainstem: the lower midbrain, upper and lower pons, and medulla oblongata. Three experts independently judged whether five tracts (corticospinal tract, medial lemniscus, medial longitudinal fasciculus, central tegmental and spinothalamic tracts) and 10 nuclei (oculomotor and trochlear nuclei, spinal trigeminal, abducens, facial, vestibular, hypoglossal, prepositus, and solitary nuclei, locus ceruleus, superior and inferior olives) on each side could be identified. In total, 240 assessments were made. The five tracts and eight nuclei were identified in all the corresponding assessments, whereas the locus ceruleus and superior olive could not be identified in 3 (1.3%) and 16 (6.7%) assessments, respectively. 3DAC-PROPELLER seems extremely valuable imaging method for mapping out surgical strategies for brainstem lesions.

Protracted delay in taste sensation recovery after surgical lingual nerve repair: a case report.

INTRODUCTION: Lingual nerve injury is sometimes caused by dental treatment. Many kinds of treatment have been reported, but many have exhibited poor recovery. Here the authors report changes in somatosensory and chemosensory impairments during a long-term observation after lingual nerve repair. CASE PRESENTATION: A 30-year-old Japanese woman claimed dysesthesia and difficulty eating. Quantitative sensory test results indicated complete loss of sensation in the right side of her tongue. She underwent a repair surgery involving complete resection of her lingual nerve using a polyglycolic acid tube containing collagen 9 months after the injury. A year after the operation, her mechanical touch threshold recovered, but no other sensations recovered. Long-term observation of her somatosensory and chemosensory function after the nerve repair suggested that recovery of taste sensation was greatly delayed compared with that of somatosensory function. CONCLUSION: This case shows characteristic changes in somatosensory and chemosensory recoveries during 7 postoperative years and suggests that taste and thermal sensations require a very long time to recover after repair surgery.

Morphologic evaluation of the inferior alveolar nerve in patients with sensory disorders by high-resolution 3D volume rendering magnetic resonance neurography on a 3.0-T system.

OBJECTIVE: The objective of this study was to evaluate the inferior alveolar nerve (IAN) morphologically in patients with symptomatic posttraumatic sensory disorders using magnetic resonance imaging (MRI) on a high-field system. STUDY DESIGN: Sixteen patients who complained of persistent sensory disturbance attributed to unilateral IAN injury participated in the investigation. High-resolution 3-dimensional volume rendering magnetic resonance neurography was performed on a 3.0-T MRI system. RESULTS: In 15 (94%) of 16 patients, high-resolution 3-dimensional volume rendering magnetic resonance neurography demonstrated morphologic abnormalities of the IAN as well as connective tissue overgrowth. These findings were confirmed intraoperatively (6 patients) and histopathologically (5 patients). The duration of sensory disturbance correlated significantly with the pattern of morphologic deformity and connective tissue overgrowth. CONCLUSIONS: The current study clearly demonstrated that appropriate application of clinical MRI techniques can significantly improve the diagnosis and potential treatment of patients with orofacial peripheral nerve disorders.

Insidious extension of pituitary prolactinoma: two can't-miss findings depicted on a 3.0-T MR system.

BACKGROUND: In this article, we present two can't-miss findings on preoperative magnetic resonance imaging (MRI) using a 3.0-T MR system resulting in a better surgical option in prolactinoma treatment after emergent of dopamine agonists. METHODS: We reviewed six cases of pituitary prolactinoma; each had vague or occult bulk of adenoma on 1.5-T MR imaging, which were finally confirmed by surgery. Four cases were preoperatively examined with a 3.0-T MR imaging system. With the 3.0-T MR system, 3-dimension-anisotropy-contrast (3DAC) MR imaging and 3-dimension fast spoiled gradient recalled acquisition in the steady state (3D-FSPGR) imaging were used for depiction of the adenoma. RESULTS: 3DAC imaging revealed cavernous sinus (CS) pathology in three cases, and multiplanar reconstruction of 3D-FSPGR imaging revealed normal pituitary gland and invasive adenoma into the CS in three cases and creeping extension up to the contralateral side of the CS invasion in four cases. CONCLUSIONS: Two can't-miss findings: (1) intrasellar creeping extension up to the opposite side of the adenoma main body and (2) intracavernous-localized adenoma with indistinct intrasellar mass should be carefully considered when neurosurgeons perform adenomectomy for patients with prolactinoma, even in cases of microprolactinoma.

Participation of primary motor cortex area 4a in complex sensory processing: 3.0-T fMRI study.

The precise movement of human fingers requires continuous and reciprocal interaction between motor and sensory systems. Similar to other primates, there is double representation of the digits and wrists within the human primary motor cortex (M1), which are generally referred to as area 4 anterior (M1-4a) and area 4 posterior (M1-4p). In this high-field (3.0 T) functional magnetic resonance imaging (fMRI) study, we hypothesized that M1-4p is more important for initiation of motion, whereas M1-4a is important for execution of a given motion involving more complex sensoriomotor interaction. We investigated M1-4a and M1-4p activation associated with two representative motor tasks, namely, finger tapping (voluntary motion, VM) and passive finger movement accomplished by continuous pressure (passive motor, PM), and two representative sensory stimulations, namely, simple stimulation of flutter vibration (simple sensory, SS), and complex stimulation by a row of pins moving either vertically or horizontally (complex sensory, CS). Both M1-4a and M1-4p were activated in both motor tasks, VM and PM. M1-4p was not activated by either of the two sensory tasks, whereas M1-4a was activated by CS but not by SS. Analysis of the center of gravities (COG) of the activated areas showed that VM and PM moved COG towards M1-4p and 3a. SS moved COG towards somatosensory cortex Brodmann areas 1, 2, and 3b, whereas CS towards M1-4a. The result clearly showed that M1-4a represents the area of secondary motor execution, which actively participates in CS processing.

Human primary motor cortex shows hemispheric specialization for speech.

Hemispheric specialization is a prominent characteristic of the human brain. Should the 'dominant' hemisphere possess differential neural organization for language production in the 'higher order' cortex, it would be rational to consider that the primary motor cortex may also show similar hemispheric specialization for speech production. In order to test this hypothesis, we investigated the spatial distribution of neural activities associated with phonation (M1p), silent tongue motion (M1t), and vocalization (M1v) within the primary motor cortex, utilizing independent component-cross correlation-sequential epoch analysis of high-field functional magnetic resonance imaging time series. While M1t showed no significant differences between the two hemispheres, M1p and M1v exhibited significant hemispheric differences. The study demonstrated direct evidence that human primary motor cortex possesses clear-cut hemispheric specialization similar to that observed for the higher order cortices.

Characterization of different paresthesias following orthognathic surgery of the mandible.

PURPOSE: Paresthesia is a well known consequence of peripheral nerve injury. However, the neural mechanisms of the 2 recognized types, spontaneous and elicited, are currently unknown. This study aimed to investigate these 2 paresthesias and the possible mechanisms accompanying orthognathic surgery. PATIENTS AND METHODS: Mechanical-touch thresholds and current perception threshold were measured before and 7 days after surgery in 60 chin sites (mental nerve area) of 30 patients who underwent orthognathic surgery. Similar testing was conducted on healthy volunteers (controls). All sites were classified by the presence or absence of each paresthesia: spontaneous paresthesia or no spontaneous paresthesia, and elicited paresthesia or no elicited paresthesia. Presence or absence analyses were followed-up for 6 weeks after surgery. RESULTS: Gender differences and maxillary surgery did not change the incidence of paresthesia during postoperative week 1 (chi-square test, P > .05). A significantly higher mechanical-touch threshold was observed with spontaneous paresthesia compared with no spontaneous paresthesia (Mann-Whitney U-test; P < .05), but not between no elicited paresthesia and elicited paresthesia (Mann-Whitney U-test; P > .05). A significant increase in postsurgery current perception thresholds values compared with presurgery values was observed at 2,000 Hz in spontaneous paresthesia, and at 2,000 and 5 Hz in elicited paresthesia (paired t test, P < .05). The incidence of spontaneous paresthesia decreased more rapidly than elicited, while the latter tended to increase again during the 6-week postsurgical test period. CONCLUSION: The results suggested that both spontaneous and elicited paresthesias are associated with damage and dysfunction in myelinated primary afferent fibers, but additional neural mechanisms are implicated during elicited paresthesia.

Efficacy of steroid treatment for sensory impairment after orthognathic surgery.

PURPOSE: Steroid hormones are therapeutic for motor and/or sensory dysfunctions caused by nerve injury. However, the timing for giving such medicine is unclear. This study aimed to estimate the efficacy of steroid treatment and determine an appropriate start time after sensory impairment. PATIENTS AND METHODS: Twenty-seven patients with sensory impairment who received orthognathic surgery were classified into groups called 1W (n = 6), 3W (n = 6), or 6W (n = 8) group on the basis of start time for steroid treatment, being 1 week, 3 weeks, or 6 weeks after surgery, respectively, and a no steroid treatment (NST) group (a control group) (n = 6) that did not receive treatment for 10 to 12 weeks after surgery. Sensory impairment was diagnosed if postoperative first week mechanical-touch threshold was over 4.0 as measured by Semmes aesthesiometer. Prednisolone treatment was administered orally to patients at 30 mg for 7 days, 15 mg for 4 days, and 5 mg for 3 days. Mechanical-touch threshold and thermal perceptions were compared before and after treatment. RESULTS: At 1 week postoperatively, there were no significant differences in mechanical-touch threshold among the 4 groups (analysis of variance, P >.05). Changes in mechanical-touch threshold in the 1W group showed no significant improvement (analysis of variance, P >.05), but in the 3W and 6W groups, there were significant differences compared with the NST group (Dunns methods, P <.05). CONCLUSIONS: Steroid treatment for sensory impairment after orthognathic surgery has the potential to accelerate recovery and it appears desirable to start treatment later than 1 week postoperatively.