Hyperthermia-induced damage to rat sciatic nerve assessed in vivo with functional methods and with electrophysiology

doi:10.1016/0165-0270(92)90073-M

Journal of Neuroscience Methods

Volume 45, Issue 3, December 1992, Pages 165-174

https://doi.org/10.1016/0165-0270(92)90073-M Get rights and content

Abstract

A 5-mm segment of the rat sciatic nerve was treated in vivo with hyperthermia (43–45°C) for different times using a brass thermode. The effect of this local heat treatment on the nerve was assessed with electrophysiology and using two functional assays. Hyperthermia led to a dose-dependent decrease of motor and sensory function. Electrophysiological examination showed a decrease in amplitude of motor and reflex responses rather than a decrease in conduction velocities. Calculated ED₅₀ values were not significantly different for the two functional and for the electrophysiological methods. Functional recovery from nerve damage took place in all cases. Measured at the same level of damage, i.e., 50% function loss, it took 14 days to recover from complete sensory function loss and 20 days from complete motor function loss. Although both motor and sensory functions were restored, 30 days after hyperthermia no responses could be detected with electrophysiology, this as a result of the thin myelin sheaths that occur upon recovery.

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INI and RH showed a similar selective inhibition effect on CAP subcomponents for slow-conducting axons, confirmed by the inhibition probability vs ΔT dose-response curve based on approximately 2000 CAP measurements. The inhibition selectivity indexes of the two heating modalities were similar across six nerves. RH only required half the total electrical power required by INI to achieve a similar ΔT.
We show that selective INI can be reproduced by other heating modalities such as RH. RH, because of its high energy efficiency and simple design, can be a good candidate for future implantable neural interface designs.
Preventing thermal osteonecrosis through 3D printed ceramic grinding tool
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Conventional grinding tools in orthopedic surgery and neurosurgery are solid in structure, leading to a limited amount of coolant that can reach the bone surgery zone, and therefore causing localized high-temperature-induced issues (infection, necrosis, and complications). Additive manufacturing allows the incomparable design and manufacturing freedoms and offers the opportunity to redesign the surgery tool to suppress the grinding temperature within a safe range. Here we present a hollow ceramic grinding tool enabled by additive manufacturing. Our CFD simulation and experiments have proved that, owing to the new design, the coolant can better reach the surgery zone, not only helping to restrict the heat accumulations, but also to remove excessive bone debris. In the in vivo test, we found that, the new design produced less apoptosis and edema area to the rat brain in comparison with the conventional tool. This design minimizes the occurrence of complications such as osteonecrosis due to high surgical temperatures, opening new opportunities for the development of orthopedic surgical tools using additive manufacturing technology.
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Citation Excerpt :
RFA of spinal OOs close to neural tissues requires rigorous attention with regard to thermal damage because neural tissues are vulnerable to heat. In experimental animal models, hyperthermia-induced sciatic nerve damage is observed following exposure to 45 °C for 15 min [20], and a distance of > 5 mm between the electrode tip and nerve root is required to avoid irreversible neural damage [21]. In one report, an increase in temperature to 48 °C at the nerve root during RFA and transient neurological impairment after RFA was reported [22].
Osteoid osteoma (OO) is a benign but painful tumour that arises from osteoblasts. Spinal lesions account for 20% of OOs. Surgical excision of spinal OO has been the standard treatment when conservative therapy is not effective. However, excisional surgery can lead to spinal instability and sometimes necessitates stabilization with spinal instrumentation. Radiofrequency ablation (RFA) is an attractive option for treating spinal OO, but thermal damage to neural tissues limits its application when the OO is located adjacent to neural tissues.
We report novel 2 cases using navigation-guided RFA for OO in the lumbar spine with a continuous cooling system for preventing neural damage. During the 5 min ablation at 90 °C, the temperature at the nerve roots adjacent to the OO was maintained at <30 °C. No neurological impairment was observed postoperatively. The symptoms caused by OO disappeared immediately after the surgery, and clinical recovery was maintained for 5 and 2 years postoperatively in Cases 1 and 2, respectively.
Direct placement of the cooling system enables both sufficient ablation and neuroprotection. The navigation system enables clinicians place the RFA probe at a precise position even in cases of OO in complex anatomical structures. To our best knowledge, this is the first report of the combined use of the navigation and cooling systems.
This novel combinatory use of navigation-guided RFA and continuous cooling will safely expand the scope of RFA application for spinal OO by preventing neural damage and preserving spinal structure.
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We identified 19 patients who developed ULP after laminoplasty with concomitant foraminotomy for radiculomyelopathy with nerve root impingement (laminoplasty with concomitant foraminotomy group [F-group]) from 4080 patients who underwent primary cervical laminoplasty at 27 affiliated institutions between 2012 and 2018. An age- and sex-matched control group comprised patients who developed ULP after laminoplasty without concomitant foraminotomy (n = 76, 4:1 ratio with F-group). Collected data included the time of onset and distribution of ULP (side and level). The site of foraminotomy was recorded in the F-group.
The F-group showed a significantly higher incidence of ULP than the candidates for the control group (15.1% vs. 3.1%, P < 0.001). The site of foraminotomy was consistent with the distribution of ULP in 79% (15 of 19 patients) of the F-group. The F-group showed a significantly higher proportion of preoperative upper-limb muscle weakness (74% vs. 37%, P = 0.005) and early-onset ULP occurring by postoperative day 1 (63% vs. 33%, P = 0.02) compared with the control group.
Our results indicate that the foraminotomy procedure in the stenotic foramen is directly involved in ULP. Combined with a previous report suggesting that early-onset ULP is associated with thermal nerve damage, our results indicate that thermal nerve damage partly explains the increased incidence of ULP in the F-group.
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Recurrent laryngeal nerve (RLN) injury is the most common and serious complication after thyroid surgery. However, little is known about the temperature threshold leading to RLN injury. In this study, we investigated threshold temperatures that cause RLN injury during thyroid surgery using continuous intraoperative neuromonitoring in swine models.
Four pigs weighing 30 to 40 kg were used for this study. We applied automatic periodic stimulation to the vagus nerve and dissected the RLN. The operative field was then filled with water at various temperatures (1.9°C to 87.4°C). The threshold temperature was defined as the temperature measured before filling the operative field that was associated with adverse events (latency increase of more than 10% or amplitude decrease of more than 50%). Loss of signal was defined as the electromyography (EMG) signal disappearing and not recovering during 30 min of observation.
The low and high threshold temperatures were 2.5°C and 81.5°C, respectively. There were no adverse events at surrounding temperatures between 5.9°C and 77.5°C. The EMG signals in the RLNs exposed to the low threshold temperatures recovered, and there was no loss of signal. In contrast, the RLNs that showed adverse events at the high threshold temperatures showed loss of signal and no recovery of EMG signals.
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Citation Excerpt :
The risk of heat-related damage of neural tissue is considerably higher compared with osseous damage. De Vrind et al.5 described the initial damage to start at 43°C with a recovery period of 30 days. Hoogeveen et al.26 found a tolerance for 30 minutes at 43°C with no detectable damage.
The main objective of the present prospective, randomized, single-blinded controlled study was to measure heat during bony decompression of lumbar spinal stenosis with high-speed drills and an ultrasonic bone-cutting knife.
Ninety patients diagnosed with lumbar spinal stenosis were included in this study and randomized for lumbar spinal canal decompression using either a high-speed drill with automatic irrigation, high-speed drill with manual irrigation, or an ultrasonic bone-cutting knife with automatic irrigation (USBCD). For evaluation of group homogeneity, a visual analog scale pain score and neurologic findings were measured preoperatively and postoperatively. Temperatures during bony decompression were measured using a forward-looking infrared camera system.
Clinical results among the 3 groups did not differ in pain reduction, improvement of neurologic findings, or the rate of complications. However, significantly lower values were found for absolute and mean maximal temperatures during bony decompression in the USBCD group compared with the groups of patients who received the high-speed drill with automatic irrigation and the high-speed drill with manual irrigation, indicating this technique to be less aggressive in terms of thermal induction of bone necrosis. USBCD allows more precise bone removal compared with high-speed drills, and despite increased device time, no significant difference in the overall decompression time was observed.
All methods examined produced short temperature peaks with possible, at least temporary, damage to bone and neural tissue. Automatic irrigation was associated with lower heat development compared with manual irrigation. Despite evidence of critical temperatures, no clinical correlation (e.g., neurologic deficits) was encountered in this study. Clinically, all 3 methods presented equally good results.

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Research paperHyperthermia-induced damage to rat sciatic nerve assessed in vivo with functional methods and with electrophysiology

Abstract

Lancet

Peptides

J. Neurol. Sci.

Exp. Neurol.

Clin. Radiol.

Exp. Neurol.

Radioth. Oncol.

J. Neurol. Sci.

Path. Res. Pract.

Int. J. Radiat. Oncol. Biol. Phys.

Int. J. Radiat. Oncol. Biol. Phys.

Exp. Neurol.

Exp. Neurol.

Reversible heat lesions with radiofrequency current: a method of stereotactic localization

J. Neurosurg.

Research paper
Hyperthermia-induced damage to rat sciatic nerve assessed in vivo with functional methods and with electrophysiology