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Biomedical subjects

Kim J Burchiel

Publications and source records attributed to Kim J Burchiel.

11 recordsLinked to original sources
PubMed2002

Trigeminal neuralgia and other neuropathic pain syndromes of the head and face.

Trigeminal neuralgia is the most common craniofacial pain syndrome of neuropathic origin. Although the diagnosis remains based exclusively on history and symptomatology, modern diagnostic techniques, particularly high-resolution magnetic resonance imaging, provides valuable new insight into the pathophysiology of these cases with additional implications for therapeutic strategies. Other neuropathic syndromes affect the trigeminal nerve and warrant different treatments with varied rates of success. Rarely, neuralgias of other cranial nerves mimic trigeminal neuralgia. Finally, it is imperative to distinguish atypical facial pains from these neuropathic syndromes to avoid unsuccessful therapies.

Facial Nerve Diseases↗
PubMed2002

An analysis of the respective risks of hematoma formation in 361 consecutive morphological and functional stereotactic procedures.

OBJECTIVE: The risk of hematoma formation in stereotactic procedures is generally considered to range between 1 and 4%, and it has been speculated that morphological procedures may have a higher risk of bleeding than functional procedures. METHODS: Between 1989 and 1999, all patients who underwent a stereotactic procedure performed by the same surgeon were enrolled sequentially onto the study. All patients had normal preoperative prothrombin time, partial thromboplastin time, and platelet count. High-resolution computed tomography or magnetic resonance imaging with a 1.5-T machine were used for the target definition. None of the patients had an angiogram before surgery. RESULTS: A total of 361 procedures was performed comprising 175 morphological procedures (139 biopsies, 18 lesion evacuations [cysts, abscesses, and hematomas], and 18 drain implantations) and 186 functional procedures (137 lesions [thalamotomy or pallidotomy], 47 deep brain electrode implantations, and two physiological explorations without lesions or implantations). There were no infections or seizures in either group. Three hematomas (1.7%) occurred in the morphological group, two of them in inflammatory lesions in immunocompromised patients (one death) and one in a pineal tumor. Three hematomas (1.6%) occurred in the functional group (no mortality). There was no statistically significant difference (P > 0.05; Fisher's exact test) in the risk of hematoma formation between morphological and functional stereotactic procedures. The morbidity and mortality related to bleeding also were not statistically different (P > 0.05; Fisher's exact test) between these two groups. CONCLUSION: In this series, the risk of bleeding was not higher for morphological procedures than for functional procedures. This suggests that the risk of bleeding for stereotactic procedures is related more to the patient than to the type of procedure performed. Our study confirms an overall risk of bleeding of 1.7% for any type of stereotactic procedure, resulting in a mortality of 0.3% and a morbidity of 1.4%.

Biopsy↗
PubMed1996

Responses of adult human dorsal root ganglion neurons in culture to capsaicin and low pH.

This study examined the responses of cultured adult human dorsal root ganglion (hDRG) neurons to protons and capsaicin, two substances known to produce pain and hyperalgesia in humans. Both substances were applied to each neuron and responses were examined under both voltage- and current-clamp recording conditions. Sensitivity to protons was tested with rapid acidification of the extracellular fluid from pH 7.35 to 6.0. In neurons nominally clamped near -60 mV, low pH evoked a transient inward current which, in all 40 hDRG neurons tested, was followed by a more sustained inward current. The sustained current was associated with an increase in membrane conductance in 10 neurons, a decrease in 27 neurons, and no overt change in conductance (< 10%) in 3 neurons. Current-clamp recordings in the same neurons showed that the proton-induced sustained net inward current caused a prolonged depolarization of the membrane potential in all 40 hDRG neurons. The prolonged depolarization was associated with action potential discharge in 5 neurons. Unlike low pH, capsaicin evoked a sustained net inward current in only a subset of neurons tested (10 nM: 1/4, 30 nM: 4/8, 100 nM: 11/18, and 10 microM: 10/10 neurons tested). The capsaicin-evoked currents were accompanied by an increase in membrane conductance in 15 neurons, a decrease in 2, and no overt change in conductance in 9 neurons. Capsaicin currents, like proton-induced currents, resulted in prolonged depolarizations (10 nM: 0/4, 30 nM: 5/8, 100 nM: 8/18, and 10 microM: 10/10 neurons tested). The depolarization resulted in the discharge of action potentials in 14 neurons. It is concluded that, while both protons and capsaicin exert excitatory effects on human sensory neurons, multiple membrane mechanisms lead to the depolarization of cultured hDRG neurons by low pH. Inhibition of resting membrane conductances contributes to the responses to low pH in some hDRG neurons.

Action Potentials↗
PubMed1992

Pain response to perineuromal injection of normal saline, epinephrine, and lidocaine in humans.

In animal neuroma models the application of alpha-adrenergic agonists causes a burst of spontaneous afferent activity. The increased activity has been hypothesized to generate nociceptive input. Corroborative work in humans, however, has not been done. Nine subjects with chronic nerve end neuromas received perineuromal injections of normal saline, epinephrine (5 micrograms), and lidocaine in a blinded manner. Qualitative and quantitative pain assessments were performed with each injection. Epinephrine, but not saline, caused an intense increase in reported pain with subjects often commenting that the appendage was "on fire". Lidocaine significantly reduced but did not completely abolish the reported pain. The chemosensitivity of the neuroma to epinephrine may explain some of the clinical responses noted after sympathetic system manipulation. It is likely that alpha-adrenergic sensitivity is only one of many components sustaining or exacerbating pain after nerve injury.

Epinephrine↗
PubMed1989

Pain responses to perineuromal injection of normal saline, gallamine, and lidocaine in humans.

Rat neurons have shown an increase of spontaneously active fibers to systemically administered potassium channel blocking agents such as tetraethylammonium chloride (TEA) and gallamine. Neuroma formation and spontaneous activity have been associated with autotomy in rats and pain in humans. To evaluate the chemosensitivity of human neurons to potassium channel blocking agents, 9 subjects with neuroma pain underwent perineuromal injection in a single-blinded fashion of normal saline, gallamine, and lidocaine. Sodium had no effect on control pain levels, while gallamine significantly increased and lidocaine significantly decreased pain from control levels. Three of 4 patients with accompanying phantom limb pain noted an increase in pain after the injection of gallamine. The data suggest that peripheral input plays a modulating but not solitary role in both neuroma and phantom limb pain. Agents which increase potassium channel permeability or decrease sodium influx would be predicted to decreased perceived pain.

Adult↗
PubMed1989

The effect of intravenous lidocaine, tocainide, and mexiletine on spontaneously active fibers originating in rat sciatic neuromas.

The effects of intravenously administered subanesthetic concentrations of lidocaine, tocainide, and mexiletine on spontaneously active fibers (SAFs) originating in 7-day-old rat sciatic neuromas were studied. Control injections of normal saline caused no decrease in SAF or discharge rate. Lidocaine and tocainide given in incremental doses of 5, 10, 15, 20 and up to 25 mg/kg caused nearly all observed SAFs to stop firing. Mexiletine given in doses of 3, 5, 7, 10 and up to 15 mg/kg showed similar results at lower doses. All agents decreased the sensitivity of SAF to mechanical stimulation. No conduction blockade occurred at these doses of intravenously administered local anesthetics. The demonstrated reduction in firing rate of SAF may explain the pain relief observed in clinical trials of these orally available agents.

Action Potentials↗
PubMed1986

Effect of intrathecal and subepineural capsaicin on thermal sensitivity and autotomy in rats.

In 79 Sprague-Dawley rats, we determined the effect of either intrathecal or subepineural capsaicin injection on: latency of withdrawal of the hind foot to a nociceptive thermal stimulus (50 +/- 1 degree C hot plate) and the onset and severity of putative behavioral evidence of chronic pain in the rat (autotomy) which commonly appears following sciatic nerve section. Capsaicin (50 micrograms) was suspended in 5 microliters of vehicle (10% Tween-80 in 0.9% saline) then injected either intrathecally at the level of the L4-5 vertebral interspace or subepineurally in the sciatic nerve at the level of the midfemur. Subepineural capsaicin consistently and efficiently produced thermal analgesia in the rat, while intrathecal capsaicin had no significant analgesic effect. In chronically denervated rats, both subepineural and intrathecal capsaicin decreased the latency to onset of first autotomy, and intrathecal capsaicin increased the severity of this behavior significantly. These data are consistent with the hypothesis that autotomy is the rat's response to abnormal sensations perceived in the denervated hind limb. Deafferentation of dorsal horn neurons appears to be of paramount importance in the production of autotomy while the relevance of peripherally originating spontaneous neuroma discharges to autotomy behavior is questioned.

Afferent Pathways↗
PubMed1984

Effects of electrical and mechanical stimulation on two foci of spontaneous activity which develop in primary afferent neurons after peripheral axotomy.

In 28 Sprague-Dawley rats, unilateral division of the sciatic nerve at the level of the midfemur was performed. Animals were observed for behavioral changes for 1-21 days, and electrophysiological recordings were made from microfilaments dissected from the ipsilateral L5 dorsal rootlets and sciatic nerve from 1 to 14 days postoperatively. Spontaneous discharges of two types were recorded: (1) variable frequency (0-100 Hz) discharges which typically occurred in rhythmic bursts and could be driven by mechanical stimulation of the neuroma; and (2) lower frequency (0.25-14 Hz) irregular activity which persisted after either excision or local anesthesia of the neuroma. The latter activity could also be recorded from the proximal cut end of the sciatic nerve following removal of the neuroma. The first type of activity was felt to be produced from the neuroma while the second originated in the region of the dorsal root ganglion (DRG). Analysis of the conduction velocities of fibers involved in each type of discharge indicated that both involved smaller myelinated filaments. However, the DRG activity involved significantly smaller fibers with conduction velocities in the A delta range. Spontaneous activity was recorded at 3 and 4 days for the neuroma and DRG activity, respectively. Ongoing discharges maximized at 7-10 days and were rare by 14 days. Autotomy of the ipsilateral foot was found to occur over a similar time course. Tetanic electrical stimulation (100 Hz) produced either little change in the baseline firing rate or prolonged afterdischarges in fibers manifesting neuroma activity. In fibers with ongoing activity of DRG origin, stimulation produced a stereotyped, brief low-frequency afterburst and then prolonged inhibition of firing. Mechanical stimulation of the neuroma produced both brief increases in spontaneous discharges and prolonged afterdischarges. In fibers with spontaneous DRG activity, minimal mechanical stimulation of their ganglion of origin produced high-frequency firing. This study demonstrates that peripheral axotomy of DRG neurons produces spontaneous activity distinct from ongoing neuroma activity in a proportion of fibers which are potentially nociceptive (A delta) as well as abnormal mechanosensitivity of the DRG. Furthermore, electrical stimulation of these fibers produces prolonged inhibition of the discharge. This finding may partially explain the prolonged relief of symptoms patients with chronic pain of peripheral origin may experience following peripheral tetanic electrical stimulation.

Animals↗
PubMedDate not supplied

Microvascular decompression.

Microvascular decompression (MVD) remains the only treatment of trigeminal neuralgia that directly addresses the presumed pathogenesis. It is a proven therapy, associated with the longest duration of pain relief while preserving facial sensation. The authors' premise for advocating early MVD is the belief that the disease's natural progression, in the absence of treatment, is toward the development of more atypical features that are refractory to treatment, signifying ongoing neuropathic injury. In an effort to more successfully select candidates for MVD, the authors have incorporated high-resolution magnetic resonance imaging into our preoperative algorithm, since it has proven extremely accurate in defining the neurovascular relations at the trigminal nerve complex. Microvascular decompression can only be recommended when it is performed with low rates of morbidity.

Decompression, Surgical↗