Brainstem Anesthesia Research Articles

A case of cardiorespiratory collapse following bilateral sub-Tenon’s blocks from brainstem anaesthesia

Sub-Tenon’s block has a superior safety profile and life-threatening complications such as cardiovascular collapse and brainstem anaesthesia are extremely rare. We report a case of cardiorespiratory collapse following bilateral sub-Tenon’s blocks at the conclusion of a laser photocoagulation procedure under general anaesthesia. The cause was most likely brainstem anaesthesia. We explore and discuss the likely mechanisms and other potential differential diagnoses. It highlights the importance of maintaining vigilance following an eye block. Attention should not falter upon completing a block or at the conclusion of a case, regardless of its type or safety profile. This case also illustrates how the presence of general anaesthesia may obscure and delay the diagnosis of brainstem anaesthesia.

Brainstem anesthesia during awake craniotomy: illustrative case.

Awake craniotomy (AC) is performed to remove the lesions near or in eloquent areas, during which the patients are alert and without any airway instrument. Apnea is a severe complication in AC. Here, the authors describe a case of sudden apnea induced by unexpected local anesthesia of the brainstem during AC. A 42-year-old male underwent AC for a large, recurrent, bilateral frontal lobe mass and experienced transient apnea and loss of brainstem reflexes during the surgery. The patient recovered spontaneous breath rhythm just a few minutes after the removal of a lidocaine cotton pledget, which was found near the patient's midbrain. Then the patient awoke and cooperated to finish the surgery. The administration of a local anesthetic subdurally in AC is common but risky. The scouring action of cerebral spinal fluid can spread those agents and cause unexpected brainstem anesthesia. A lower concentration of the anesthetic and keeping away from the cistern can make it safer.

Brainstem Anesthesia after Retrobulbar Anesthesia in Cataract Surgery: A Case Report

Brain-stem anesthesia is a serious and rare complication of orbital regional anesthesia that may occur when the local anesthetic agent gains access to the central nervous system via a direct spread from the apex of the orbit or the submeningeal pathways. We report the case of a 66 -year-old man who developed, after a retro-bulbar block for cataract surgery, a tonico-clonic seizures, hypotension and bradycardia-features of brainstem anesthesia. We present the clinical features, treatment and comments on how to prevent the problem. Although it is rare, and because it may be life-threatening in some cases, physicians who perform retrobulbar block should be aware of its features and various clinical manifestation in order to recognize and treat it. Also, facilities where ophtalmic surgery under local anesthesia are performed should be properly equiped in order to manage this complication.

Possible Brainstem Anaesthesia in a Cat after Ultrasound-Guided Retrobulbar Block

A 13-year-old neutered, blue-eyed female Siamese cat with a bodyweight of 4.8 kg was admitted for enucleation of the right eye. An ultrasound guided retrobulbar block with 1 mL of ropivacaine was performed under general anaesthesia. When the tip of the needle was visualised inside the intraconal space, negative aspiration of the syringe before injection and no obvious resistance during injection were confirmed. Instantly, after ropivacaine was administered, the cat became apnoeic, and its heart rate and the blood pressure increased significantly for a short period of time. During surgery, the cat needed cardiovascular support to maintain blood pressure and was under continuous mechanical ventilation. Spontaneous breathing returned 20 min after the end of anaesthesia. Brainstem anaesthesia was suspected, and after recovery, the contralateral eye was examined. A reduced menace response, horizontal nystagmus, mydriasis, and absence of the pupillary light reflex were present. The following day, mydriasis was still present, but the cat was visual and was discharged. The inadvertent intra-arterial injection of ropivacaine was suspected to be the cause of the spread into the brainstem. To the current authors' knowledge, possible brainstem anaesthesia has only been reported in a cat 5 min after a retrobulbar block but never instantly.

Apnea caused by retrobulbar anesthesia: A case report

Apnea caused by retrobulbar anesthesia is a very rare but severe complication during ophthalmic surgery. We report a rare case of apnea caused by retrobulbar anesthesia, and emergency resuscitation was used. A 74-year-old female patient was diagnosed with rhegmatogenous retinal detachment in the right eye and planned to undergo vitrectomy under retrobulbar anesthesia. After the retrobulbar anesthesia in her right eye, she became unconscious and apneic. It was suggested that she had developed brainstem anesthesia. Assisted ventilation was initiated. Atropine 0.5 mg, epinephrine 1 mg, ephedrine 30 mg, and lipid emulsion were given. Five minutes later, her consciousness and breathing gradually returned, but with uncertain light perception in her right eye. Alprostadil 20 µg was given, and after 2 h her visual acuity resumed to the preoperative level. Brainstem anesthesia is a serious complication secondary to retrobulbar anesthesia. Medical staff should pay attention to the identification of brainstem anesthesia and be familiar with the emergency treatment for this complication.

Computed tomography scan measurements of the globe and orbit to assess the risks of traumatic complications from medial peribulbar anaesthesia

Complications of peribulbar anaesthesia include retrobulbar haemorrhage, globe perforation and brainstem anaesthesia. Therefore, this study took measurements relating the proximity of medial canthus to the optic nerve and also the safe angle between orbit and globe using 200 multiplanar reconstructed computed tomography (CT) images of the orbit. The principal results show that in 1.5% of the sample, the optic nerve is within 20 mm of the medial canthus, with a minimum distance of 15 mm. One% have a safe angle of 10 degrees or less between bone and globe. None of the demographic data, nor axial length were predictive of these results. We have shown that there are a minority of patients with unusual orbital anatomy. This places them at a theoretical higher risk of complications. These cases are not currently predicted by measured data.

Efficacy of Retrobulbar versus Topical Anesthesia in Cataract Surgery

Aim: To monitor the effect of retrobulbar versus topical anesthesia in cataract surgery patients by comparing different parameters such as: intraocular pressure akinesia and analgesia parameters. Study type: Interventional case series. Place and duration of study: Department of Ophthalmology, Niazi Medical & Dental College Sargodha from 1st October 2020 to 31st October 2021. Methodology: One hundred patients who underwent cataract surgery were enrolled. Study participants were divided into two groups and each group contain fifty 50 participants. Group one give retrobulbar block and group two treated by topical anesthesia. Complete ocular and systematic examinations and relevant examinations like clotting time, blood pressure, blood sugar, complete blood examination and bleeding time were done before starting the surgery. Results: 80% were males and 20% were females. During topical local anesthesia, 47(94%) patients experienced pain free surgery whereas in retrobulbar anesthesia, only 38(76%) patients experienced pain free surgery. In retrobulbar anesthesia group, complete akinesia was observed in 25(50%) patients. In retrobulbar group, significant increase in intraocular pressure was noted 41(82%) upto 30 mmHg after the administration of local anesthesia as compared to topical anesthesia group. Conclusion: Topical anesthesia is more safe and effective approach for cataract patients in contrast to retrobulbar group. It prevents many life and sight threatening implications like globe perforation and brain stem anesthesia. Key words: Efficacy, Retrobulbar, Topical anesthesia, Surgery

Brainstem anesthesia: A rare complication after peribulbar anesthesia

Brainstem anesthesia (BSA) is a rare but serious complication of the peribulbar block. Fewer than ten cases have been reported in the literature. We report a case of BSA after the peribulbar block for cataract surgery. The patient developed convulsion and respiratory arrest 5 min after injection of 7 ml of 2% lignocaine using a 25 ml (mm) length of 24 gauge (G) needle. The patient was successfully managed with prompt recognition and mechanical ventilation for about 1 h. Cataract surgery was performed 3 months after the adverse event. This time, the patient had an uneventful recovery. The patient was well at the 6-month follow-up.

Ultrasound detection of iatrogenic injury during peribulbar eye block: a cadaveric study

BackgroundOphthalmic eye blocks, such as retrobulbar, peribulbar and sub-Tenon’s, are traditionally conducted “blind”. Complications are rare but potentially devastating. Life-threatening complications include brain stem anesthesia and local anesthetic toxicity, whereas...

Unintentional brainstem anesthesia after prolonged sub-tenon block. Сase report

A 64-year-old ASA 2 woman, with left eye retinal detachment was admitted for pars plana vitrectomy. There were no any neurological diseases, stroke, angina, myocardial infarction, epilepsy and allergy in her medical history. There aren’t clinical significant changes in her blood tests and ECG. General anesthesia was induced and maintained with inhalation of sevoflurane on target value of MAC 0.9–1.1. Analgesia was maintained by prolonged Sub-Tenon block — 1 % lidocaine 2 ml/h through catheter. The duration of surgery was 215 minutes. Sevoflurane and lidocaine were stopped immediately after the end of the surgery. The effective spontaneous breath has been noted by the first minute after surgery. However, the delayed recovery wasn’t allowing to discharge the patient from operating room within 50 minutes and the drowsiness was persisted 1.5 hours more after this. There wasn’t any neurological deficiency, the hemodynamic was stable and the patient had an effective breath during this time and later in postoperative period. With the exception of a possibility of inadvertent intravenous introduction of local anesthetic and development of systemic toxicity, the most probable cause of this complication was the brainstem anesthesia. The possibility of brainstem anesthesia in ophthalmology is well described when using retrobulbar and peribulbar anesthesia. The described cases of this complication of Sub-Tenon block are single. Our case presented a serious adverse event of prolonged Sub-Tenon block without life treating symptoms and neurologic consequences.

Ocular Anesthesia-Related Closed Claims from Ophthalmic Mutual Insurance Company 2008–2018

To evaluate the types of anesthesia-related closed claims and their contributing factors, using data from the Ophthalmic Mutual Insurance Company (OMIC). Retrospective analysis of preexisting data. Plaintiffs who filed a professional liability claim or suit (written demand for money) against OMIC-insured ophthalmologists, ophthalmic practices, or surgicenters in which the surgical case occurred. Plaintiff claims were collected from the OMIC database from 2008 to 2018 using search queries for terms associated with known complications of ophthalmic anesthesia. Number and types of anesthesia-related injuries and claims, who administered the anesthesia, the outcomes of the claim or suit, cost to defend, and payments made to plaintiffs. Sixty-three anesthesia-related claims or suits were filed by 50 plaintiffs. Anesthesia-related injuries included globe perforation (n= 17), death (n= 13), retrobulbar hemorrhage (n= 7), optic nerve damage (n= 4), vascular occlusions (n= 2), pain (n= 2), eye or head movement resulting in injury (n= 2), and 1 case each for numbness, diplopia, and tooth loss during intubation. All but 1 patient who died had preexisting, significant comorbidities. Two deaths were related to brainstem anesthesia. Regarding the type of anesthesia in the closed claims, retrobulbar and peribulbar anesthesia were the most common types (n= 16 each), followed by local infiltration around the lids and facial nerve (n= 6), topical anesthesia (n= 5), and general anesthesia (n= 5). In 2 cases, the exact type of anesthesia was unknown but not general. The 5 topical with sedation anesthesia-related claims were due to inadequate pain control (n= 2), ocular movement resulting in capsular rupture (n= 2), or death (n= 1) allegedly related to excessive or inadequate monitoring of sedation. There were 5 claims related to general anesthesia including 4 deaths and 1 tooth loss during intubation. Sedation was alleged to be a factor in 5 cases resulting in death. Anticoagulants were a factor in 3 retrobulbar hemorrhage cases. Although claims and suits were infrequent given the large number of insured ophthalmologists and the large number of surgical cases requiring various types of anesthesia performed over the 10.5-year study period, severe injuries can occur.

Brainstem Anaesthesia after Retrobulbar Block.

Regional anaesthesia techniques in ophthalmology are usually utilized for day case surgery. During various procedures, profound akinesia of the eye and anaesthesia of the surgical site are required, both of which are achieved with retrobulbar block. Due to the anatomy of the eye, life-threatening complications are possible. An 82-year-old female with secondary post-herpetic uveitic glaucoma of the right eye presented at the Department of Ophthalmology for an elective trans-scleral laser cyclophotocoagulation. She was given a retrobulbar block to the right eye with 2 mL of 0.5% levobupivacaine and 2 mL of 2% lidocaine. The procedure was technically performed without any issues. 2-3 minutes after the injection she became lethargic and 5 minutes later she lost consciousness and developed severe hypotension with bradycardia and respiratory arrest. She was successfully intubated and resuscitated, using mechanical ventilation, vasoactive medications, fluid therapy and intravenous lipid emulsion. There are three mechanisms for local anaesthetic (LA) to reach the central nervous system after a retrobulbar block: systemic absorption of LA, direct intra-arterial injection and retrograde flow into the cerebral circulation, and injecting LA into the subdural space via puncturing the dural optic nerve sheath, the latter being most common. The clinical picture of our patient was very consistent with subdural anaesthesia after exposure of the pons, midbrain and cranial nerves to LA, i.e. brainstem anaesthesia. Following appropriate life support measures taken in our case, there was a successful outcome. To minimize the chance for brainstem anaesthesia after retrobulbar block, we recommend low volume with low concentration of LA and block performance by an experienced ophthalmologist or anaesthesiologist with proper technique. Patients receiving retrobulbar anaesthesia should be carefully monitored at least 20 minutes after the block. Life support equipment should be available before performing retrobulbar block.

Efficacy and Safety of a Novel Blunt Cannula Trans-Sub-Tenon's Retrobulbar Block for Vitreoretinal Surgery.

PURPOSE:To evaluate a novel trans-sub-Tenon's retrobulbar block (TSTRB) compared to sub-Tenon's block (STB) and peribulbar block (PBB) anesthesia for vitreoretinal surgery.METHODS:This study was a prospective evaluation of cases undergoing TSTRB, STB, or PBB. The Kallio scale and Brahma scales were used to score hemorrhage and extraocular motility, respectively. Pain was documented on a visual analog score graded (1–10) at induction, intraoperatively, and postoperatively, any confounding variables were noted.RESULTS:Seventy eyes have been used in this analysis, of which TSTRB was used in 37% (n = 26), PBB in 34% (n = 24), and STB in 29% (n = 20). Postoperative analgesia was required by 10% (n = 2) of STB and 8% (n = 2) of PBB; none of the TSTRB cases required analgesia (P = 0.003). The mean volume required with each technique was as follows: TSTRB, 4.8 ml; STB, 5.3 ml; and PBB, 10.4 ml (P = 0.030). The volume of anesthesia was correlated with the level of proptosis and even more important affected the ease of surgery most (P = 0.005). Akinesia was greatest with TSTRB > PBB > STB (P = 0.040). There were no complications such as brainstem anesthesia, globe perforation, or retrobulbar hemorrhage.CONCLUSION:Intentionally extending a STB into the retrobulbar space, via a TSTRB fenestration utilizes a familiar skill set. TSTRB produced the best levels of reduced kinesia during surgery and increased duration of postoperative analgesia. The technique uses a small-volume anesthesia.

Potentially life-threatening consequences of peribulbar anesthesia

Peribulbar anaesthesia is the most commonly used anaesthesia for intraocular surgeries, especially glaucoma and vitreoretinal surgeries. We present a case of a 70 years old man who became unconscious and developed other signs of brainstem anaesthesia following peribulbar block for a combined glaucoma and cataract surgery. Complications with peribulbar anaesthesia are remote but possible. Patients undergoing ocular surgeries under peribulbar anaesthesia should be closely monitored and facilities to tackle such life threatening complications must be available in the operation theatre.

Dexmedetomidine was Better at Lowering Intraocular Pressure than Magnesium when Combined with Local Anesthetics in Peribulbar Blocks for Posterior Segment Eye Surgery

Background and Aim: Many medications are combined with local anesthetics for peribulbar blocks to improve the quality of the block, however, few studies have compared the effect of dexmedetomidine and magnesium on intraocular pressure when combined with local anesthetics which was the primary endpoint of this double blinded study. Materials and Methods: A randomized controlled clinical trial was conducted on 60 ASA Physical Status (ASA PS) I-II patients scheduled for elective posterior segment eye surgeries under peribulbar anesthesia. Patients were randomly allocated to one of three groups of 20 each according to the medications they received. Local anesthetic solution was prepared using 8 ml of bupivacaine 0.5% and lidocaine 2% in a 1: 1 ratio plus 1ml of hyaluronidase (150 units) making a total volume of 9 ml: Group D received: local anesthetic + 20 µg dexmedetomidine diluted with 1 mL of normal saline. Group M received: local anesthetic + magnesium sulphate 50 mg in 1 ml normal saline. Group C received local anesthetic + 1 ml normal saline. Intraocular pressure was measured with the Perkins applanation tonometer immediately before injection and at 1, 5, 10, 15 minutes (min) after injection and then at the end of the procedure, the onset and duration of lid and globe akinesia were assessed. Postoperative analgesia and the first dose of analgesic medication were also assessed. Results: Intraocular pressure measurements were statistically lower in group D than the other two groups at 10 and 15mins. The onset of globe and lid akinesia was the most rapid in Group D compared to the other two groups. The duration of globe and lid akinesia was the longest in group D. Time to first analgesic dose request was significantly longer in group D followed by group M then group C. Visual analogue score for pain was significantly less between group D and other two groups. There were no episodes of hypotension or bradycardia in the three groups. No side effects or complications as hemorrhage, globe perforation, brain stem anesthesia sedation were observed. Conclusion: In our study addition of dexmedetomidine to a peribulbar block was statistically better at reducing IOP, increasing the duration of optic anesthesia and delaying the need for postoperative analgesic dose request than magnesium.

Magnesium sulphate versus Dexmedetomidine as adjuvants for local anasthetics in peribulbar block for eye surgeries: Clinical comparative study

Background: Regional anesthesia is a preferred technique for ophthalmic surgery. It is safe, inexpensive and provides efficient ocular anesthesia for ophthalmic surgery. It is associated with less hemodynamic instability, less respiratory depression, better postoperative pain relief, and less nausea and vomiting compared to general anesthesia. Among regional blocks, peribulbar block is safer in comparison with retrobulbar block due to a lesser incidence of serious complications such as brain stem anesthesia, globe perforation, and retrobulbar hemorrhage. Objective: The aim of the study was to compare the safety and efficacy of the use of Magnesium sulfate versus that of Dexmedetomidine as an adjuvant to the local anesthetic in peribulbar anesthesiaas for inducing optimal operating conditions for eye surgery in terms of akinesia (as a primary end point), analgesia, incidence of complications, as well as patient and surgeon satisfaction (as secondary end points). Patients and Methods: The present study included 50 patients (females and males) aged 20-80 years. Materials: Anesthetic drugs, Needles size: 25 gauge, Intravenous cannula 22 G, Drugs for premedications: intravenous midazolam (5mg/ml, Mediathetic, Amoun, Egypt) (0.01mg/kg) and Fentanyl Citrate (50µg/ml, Fentanyl- Janssen, Belgium) (25 µg)was administrated 5minutes before the block, Monitors for vital signs registration were done for each of the following: Electrocardiograph (ECG), non-invasive blood pressure (NIBP), heart rate (HR) and oxygen saturation (SpO2), respiratory rate (RR), Anesthetic machine, resuscitation equipment and drugs. Results: The current study was carried on 75 patients divided into Three equal groups: first group (control group), second group (dexmedtomedine group) and third group (magnesium sulphate group). All patients were scheduled for surgery. Conclusion: Addition of 50 mg of magnesium 10% or 15 mic of dexmedetomidine to local anesthetic mixture for peribulbar anesthesia in the operations of phacoemulsification of cataract and intraocular lens implantation accelerated onset of globe anesthesia, akinesia of the globe and the lid, prolonged the duration of globe akinesia, lid akinesia, time to 1st analgesic request, and enhanced the satisfaction of the patients and quality of the operative conditions.

Postoperative analgesia of ultra-low-dose naloxone versus dexmedetomidine with local anesthetic in peribulbar block in cataract surgery

Background and aim Regional anesthesia in eye surgery is a preferred technique and widely used in all eye surgery centers. It is safe, inexpensive, simple, and reliable and provides efficient ocular anesthesia. It is associated with less complications than general anesthesia. Among regional blocks, peribulbar block is safer in comparison with retrobulbar block owing to lesser incidence of complications such as retrobulbar hemorrhage, globe perforation, and brain stem anesthesia, but it has some disadvantages such as incomplete orbital and eyelid akinesia and decrease time of analgesia in which the patient need pain relief postoperatively, so many adjuvant drugs have been added to local anesthetic to overcome these disadvantages. Dexmedetomidine is a central-acting drug, a highly selective α2-agonist, that has been used as an additive to local anesthetic, whereas the mechanism of action of ultra-low-dose naloxone includes inhibition of impulses of the excitatory opioid receptors and release of encephalin. The goal of this study was to assess the effect of ultra-low-dose naloxone and dexmedetomidine as adjuvants for local anesthetic on duration of analgesia as primary outcome and akinesia of the globe and eyelid and occurrence of complications as a secondary outcome. Patients and methods A total of 60 patients were included in this prospective randomized double-blind clinical study scheduled for elective cataract surgery, who were randomly divided into two groups: N group (n=30) received 3.5 ml of lidocaine 2%, 3.5 ml of bupivacaine 0.5% with 15 IU/ml hyaluronidase for both lidocaine and bupivacaine, and 100 ng naloxone in 1 ml normal saline. D group (n=30) received 3.5 ml of lidocaine 2%, 3.5 ml of bupivacaine 0.5% with 15 IU/ml hyaluronidase for both lidocaine and bupivacaine and 25 μg of dexmedetomidine in one-ml normal saline. The assessment includes duration of analgesia (h), which is the time from injection till visual analog scale of more than 4 or request of analgesia by the patient, akinesia of the globe and eyelid assessed every 2 min using a three-point scale, and occurrence of complications (pain during injection, chemosis, diplopia, bradycardia, and hypotension). Results A total of 60 cataract surgery patients were included in the study. Regarding primary outcome (duration of analgesia), we found a highly statistically significant difference in duration of analgesia, with longer duration of analgesia in N group of patients compared with D group (P Conclusion The addition of ultra-low-dose naloxone to local anesthetic in cataract surgery shows longer duration of analgesia.

Brainstem anaesthesia following intranasal packing with lignocaine and adrenaline.

Brainstem anaesthesia following intranasal packing with lignocaine and adrenaline.

Exudative Retinal Detachment Associated with Complicated Retrobulbar Anesthesia

Retrobulbar anesthesia (block) is used for many ocular surgeries, whereas it is well known that this procedure has complications such as for retrobulbar hemorrhage, globe perforation, optic nerve injury and brain stem anesthesia. In this report, we present a unique case in the literature of isolated exudative retinal detachment (RD) secondary to iatrogenic retrobulbar hemorrhage. A 73-year-old woman underwent retrobulbar block for combined phaco-vitrectomy. Immediately after the injection, progressive proptosis was recognized. The globe was decompressed and she underwent combined phaco-vitrectomy after stabilization of the eye on the same day. At the be-ginning of the vitrectomy, a dome shaped serous RD was observed in the infero-temporal quadrant. Peripheral exploration was performed, whereas there was no retinal tear or hole. On the first day postoperatively, serous RD was disappeared. In conclusion, this report suggests that increased intraorbital pressure secondary to iatrogenic retrobulbar hemorrhage might lead exudative RD.

Glutamate dysregulation in the trigeminal ganglion: A novel mechanism for peripheral sensitization of the craniofacial region

In the trigeminal ganglion (TG), satellite glial cells (SGCs) form a functional unit with neurons. It has been proposed that SGCs participate in regulating extracellular glutamate levels and that dysfunction of this SGC capacity can impact nociceptive transmission in craniofacial pain conditions. This study investigated whether SGCs release glutamate and whether elevation of TG glutamate concentration alters response properties of trigeminal afferent fibers. Immunohistochemistry was used to assess glutamate content and the expression of excitatory amino acid transporter (EAAT)1 and EAAT2 in TG sections. SGCs contained glutamate and expressed EAAT1 and EAAT2. Potassium chloride (10mM) was used to evoke glutamate release from cultured rat SGCs treated with the EAAT1/2 inhibitor (3S)-3-[[3-[[4-(trifluoromethyl)ben zoyl]amino]phenyl]methoxy]-l-aspartic acid (TFB-TBOA) or control. Treatment with TFB-TBOA (1 and 10μM) significantly reduced the glutamate concentration from 10.6±1.1 to 5.8±1.4μM and 3.0±0.8μM, respectively (p<0.05). Electrophysiology experiments were conducted in anaesthetized rats to determine the effect of intraganglionic injections of glutamate on the response properties of ganglion neurons that innervated either the temporalis or masseter muscle. Intraganglionic injection of glutamate (500mM, 3μl) evoked afferent discharge and significantly reduced muscle afferent mechanical threshold. Glutamate-evoked discharge was attenuated bythe N-methyl-d-aspartate receptor antagonist 2-amino-5-phosphonovalerate (APV) and increased by TFB-TBOA, whereas mechanical sensitization was only sensitive to APV. Antidromic invasion of muscle afferent fibers by electrical stimulation of the caudal brainstem (10Hz) or local anesthesia of the brainstem with lidocaine did not alter glutamate-induced mechanical sensitization. These findings provide a novel mechanism whereby dysfunctional trigeminal SGCs could contribute to cranial muscle tenderness in craniofacial pain conditions such as migraine headache.