Georg Feigl

Comparison of fresh and Thiel’s embalmed cadavers according to the suitability for ultrasound-guided regional anesthesia of the cervical region

IntroductionUltrasound-guided punctures are a new technique in anesthesia. However, training in these techniques requires conditions resembling real life as far as possible for learning purposes. Several models are available, but none associates realistic anatomy and lifelike sensations of the passage of fascias. The aim of our study was to compare fresh and Thiel’s embalmed cadavers for ultrasound-guided punctures.MethodsEight fresh cadavers and eight Thiel’s embalmed cadavers were investigated. The cervical region was scanned with an ultrasound probe. Age, sex and body mass index (BMI) were recorded. Visibility of he structures, including sternocleidomastoid (SCM) muscle, anterior and middle scalene muscles, thyroid gland, nerve and the needle, was evaluated as 0 (not visible or bad visibility) or 1 (good visibility). The feeling (“pop”) of passing the fascias was noted as 0 (not felt) or 1 (felt). The possibility of nerve displacement with the needle, the difficulty of intraneural injection and the possibility of nerve penetration and nerve swelling were all recorded as 0 (not possible) or 1 (possible).ResultsThe two groups were comparable in terms of sex, age and BMI. Visibility of the SCM muscle and the needle was better in the Thiel group. Moreover, the “pop” feeling and nerve swelling were significantly more frequently present in the Thiel group. There was no significant difference in terms of the other results between the two groups.ConclusionsCadavers embalmed according to Thiel’s method should be recommended for ultrasound-guided punctures as a realistic and lifelike model.

Eye movements in response to electrical stimulation of the lateral and superior ampullary nerves.

Objectives: Recently, we demonstrated that it was possible to elicit vertical eye movements in response to electrical stimulation of the posterior ampullary nerve. In order to develop a vestibular implant, a second site of stimulation is required to encode the horizontal movements. Methods: Three patients with disabling Menieres disease were included in the study. Before a labyrinthectomy via a standard transcanal approach was performed, their lateral and anterior ampullary nerves were surgically exposed under local anesthesia through a procedure we recently developed. The attic was opened, the incus and malleus head were removed, and a small well was drilled above the horizontal portion of the facial nerve canal to place an electrode. This electrode was used to deliver balanced biphasic trains of electrical pulses. Results: The electrical stimuli elicited mainly horizontal nystagmus without simultaneous stimulation of the facial nerve. Conclusions: It is possible to stimulate electrically the lateral and superior ampullary nerves without simultaneous stimulation of the facial nerve. Because the nerves run close to each other, electrical stimulation provoked eye movements that were not purely horizontal, but also had some vertical components. Nevertheless, this site can be used to encode horizontal movements, because central adaptation may correct unnatural afferent vestibular cues delivered by a prosthetic sensor. The range of stimulus intensities that produced a response was broad enough for us to envision the possibility of encoding eye movements of various speeds.

A comparison of two emergency cricothyroidotomy kits in human cadavers.

BACKGROUND:We compared two emergency cricothyroidotomy kits designed to avoid lesions during insertion, one based on the Seldinger technique (ST), the other based on the concept of a mechanical detection of the posterior wall of the larynx, with regard to insertion time, success rate, and complication rate. METHODS:Cricothyroidotomy was performed under fiberoptic control in 40 human cadavers embalmed according to Thiel’s technique. The set chosen for use was randomized: new technique (NT) or ST. Duration of the procedure, success rates, and incidence of laryngeal injuries were compared. Traumatic lesions observed with the fiberoptic bronchoscope were anatomically confirmed after dissection. RESULTS:The two groups had comparable epidemiological and anatomical records. Cricothyroidotomy was performed faster with the NT than with the ST (median 54 vs 71 s, P = 0.01). Failure rates were comparable between groups (4 vs 1, P = 0.34), and there were fewer major complications in the posterior tracheal wall with the ST (0 vs 8, P = 0.003). In the ST group, only minor punctiform lesions of the posterior trachea wall were observed in four cases. CONCLUSIONS:In this model, despite a shorter insertion time, the NT produced more lesions and more failures than the ST.

Is Thiel's embalming method widely known? A world survey about its use

IntroductionThiel’s embalming technique, first described by Thiel in 1992, conserves texture and colour in cadavers close to that observed in the living. It would appear that few anatomy laboratories use this method, and literature describing its use worldwide is sparse. The aim of our study was to conduct a worldwide survey on the use of this method.MethodsA questionnaire was sent out by mail to 311 anatomy laboratories or institutes across the five continents. There were six multiple choice questions to assess the level of awareness of Thiel’s method, the frequency of its use among respondent institutions, the most frequently used solutions for conservation of cadavers and perceived obstacles to the use of Thiel’s technique.Results109/311 (35%) centres replied to the questionnaire; 56% of centres had previously heard of Thiel’s technique, but only 11 centres (10% of respondents) used it regularly, and all of these were in Europe. Formalin remains the most widely used conservation solution around the world.ConclusionsThiel’s embalming technique is not widely known, and therefore, little used. The main obstacle to its wider use is likely the language barrier, since most of the publications describing Thiel’s method are in German, which is not widely spoken outside of a few European countries.

Flexibility of Thiel’s embalmed cadavers: the explanation is probably in the muscles

IntroductionThe flexibility of cadavers conserved using Thiel’s embalming method remains unexplained. We aimed to perform microscopic comparison of muscle and tendon fibres from fresh cadavers (FC), formaldehyde-preserved cadavers (FPC) and cadavers conserved by Thiel’s method (TC).MethodsMuscle and tendon biopsies performed on FC, FPC and TC were conditioned and stained by Masson’s trichrome, Sirius red and Ramon y Cajal, then studied under optical microscope. Alignment and integrity of the muscle and tendon fibres were studied.ResultsWe observed a modification of the muscle fibres in all specimens from TC, regardless of the type of staining used. The muscle fibres taken from FC and FPC were relatively well conserved, both in terms of alignment and integrity. We did not observe any modification of collagen in either muscle or tendon fibres.ConclusionsThe considerable fragmentation of the muscle proteins, probably caused by certain corrosive chemicals, (e.g. boric acid) present in Thiel’s embalming solution, could explain the suppleness of the TC. However, we cannot exclude the possibility of alterations in tendon or muscle collagen, since the experimental methods we used, did not allow for the study of collagen ultrastructure.

Superior vestibular neurectomy: a novel transmeatal approach for a denervation of the superior and lateral semicircular canals.

Objective: To assess morphologically a transmeatal approach to the lateral and superior ampullary nerves performable under local anesthesia and simultaneously with the existing approach to the singular nerve developed by Gacek during the same operation. Materials and Methods: Eighty halves of human heads preserved with the Thiel method were operated on by an otologist. Two surgical approaches were tested on each specimen, 1 superior and 1 inferior to the tympanic segment of the facial nerve. The 80 specimens were divided into 2 groups. In the first group, the osseous canal of the nerves of the lateral and superior semicircular canal were previously probed and next operated. In the second group, the osseous canal of the nerves were operated prior assessment by dissection. Afterward, all 80 halves underwent computed tomographic investigation to measure the distance between the entrance point of the drill in the medial wall of the tympanic cavity and the osseous canal the ampullary nerves. Results: Inferior approach to the canal of the nerves could not be done without wide opening of the vestibulum in all 80 specimens. In the superior approach, the nerve could be reached directly in 5 cases, and only via the osseous ampulla of the lateral semicircular canal in 28 cases in the first group. In 7 cases, the nerves could not be reached without damage to the membranous labyrinth. In the second group, the nerve could be reached directly in 2 cases, via the osseous ampulla in 36 cases, and was unreachable in 2 cases. Significantly, distances longer than 3 mm between the surgical access and the nerve were found on the inaccessible cases. Conclusion: A transmeatal approach is possible superiorly but not inferiorly to the facial nerve, although it is necessary to open the osseous ampulla but not the membranous labyrinth in most cases.

Transcanal approach to the singular nerve.

Objectives/Hypothesis: Intractable benign paroxysmal positional vertigo is rare, and surgery is indicated in only a very small number of cases. Transcanal singular neurectomy is considered a difficult and risky procedure possibly leading to hearing loss and vertigo. The objective of this study was to evaluate the feasibility of the singular neurectomy through the external ear canal in an attempt to explain the contradictory results of previous reports of anatomists and of surgeons who abandoned the technique, considering that the singular neurectomy could not be reached via the external auditory canal without damaging the labyrinth. Materials and Methods: Anatomical study on 100 halves of human heads in which the canal of the singular nerve (SN) was identified and opened at its extremities, the internal auditory canal and the ampulla of the posterior semicircular canal, via a posterior fossa approach. Next, the canal of the SN was dissected via the external auditory canal, at the floor of the round window (RW) niche. The relation of the SN canal to the ampulla of the posterior semicircular canal was evaluated. Results: In 90 cases, the canal was transected medially to and away from the ampulla of the posterior semicircular canal, and in 8, at its emergence from the posterior ampullary recess. In these 98 cases, the RW membrane and the bony labyrinth were kept intact. In two cases, the canal of the SN could not be reached at the floor of the RW niche. Conclusion: Singular neurectomy is feasible via the external auditory canal, without damaging the RW membrane or the labyrinth in 98% of the cases. Because singular neurectomy is indicated in a very small number of cases, it is difficult to master this particular surgical procedure. This may explain why most surgeons abandoned the technique after a few attempts, followed by an unacceptable rate of sensorineural hearing loss

Development of surgical skill with singular neurectomy using human cadaveric temporal bones.

BACKGROUNDnProfound anatomical knowledge and surgical experience are essential for safe otological surgery. The surgeons learning curve is evaluated in performing Gaceks singular neurectomy on cadaveric specimens.nnnMATERIALS AND METHODnOne otological surgeon performed Gaceks approach on 96 halves of human heads embalmed according to Thiels method, divided into four groups (24 halves per group) and evaluated them concurrent to the evaluation of an anatomist after a first surgical attempt. Successful operations were subdivided into direct hits of the osseous canal of the posterior ampullary nerve also known as the singular nerve and indirect hits with access to the posterior ampullary recess. Unsuccessful operations showed no hit of the nerve without lesion of the membranous labyrinth. Indirect or no hits were reinvestigated in a second attempt to evaluate possible reclassifications due to a learning process of the surgeon. The order of dissection, the rate of success and the changes of results in correlation with the numbers of dissected specimens were documented.nnnRESULTSnThe success rate significantly increased from 54.2% direct hits after the first group to 87.36% in the fourth group after the first attempt. Successful operations were performed in 86.5% after completion of the first attempt and 97.9% after the second attempt. The number of new allocations decreased from 11 cases in the first group of dissected specimens to zero in the fourth group.nnnCONCLUSIONSnThis paper strengthens the value of cadaveric training for surgeons and the crucial role of dissection of a large number of specimens in improvement of the surgeons experience and success rate.

A new anatomical technique to investigate nerves by imagery

IntroductionWe describe a novel post mortem technique that makes it possible to visualise the nerve structure of the brachial plexus using imaging.Materials and methodsWe dissected in situ the brachial plexus of a cadaver preserved by formaldehyde. A preparation composed of a mixture of baryte powder, water and colorant, was applied to all sides of the brachial plexus and blood vessels of the region under study. A high resolution CT scan was performed. With the aid of Mimics (Materialise) software, segmentation of all the nerve and vascular structures on each of the 650 slices obtained was performed. The Mimics software then compiled all the slices to generate a 3-dimensional STL image.ResultsThe image obtained was printed with a stereolythography printer, to produce a plastic model representing part of the cervico-thoracic spinal cord, the ribs, sternum, scapula, humerus, and clavicle, with the left brachial plexus and the subclavian, axillary and brachial veins and arteries.ConclusionsThis technique has the potential for a wide range of uses: for teaching anatomy, to improve teaching of medical techniques, 3-dimensional modelisation of other nerve structures. The advantage is that the model obtained is a faithful and realistic reproduction.

Die Bedeutung der Fascia stylopharyngea bei intraoralen Blockadetechniken

ZusammenfassungHintergrundMittels transoraler Blockade des Ganglion cervicale superius des Truncus sympathicus kann bei Trigeminusneuralgien durch Ausbreitung eines Opioids bis zum N.xa0mandibularis eine zusätzliche Schmerzreduktion erzielt werden. Das Vorhandensein der Fascia stylopharyngea senkt möglicherweise die Erfolgsrate. Durch genaue anatomische Untersuchung der Faszie wollen wir auf die Effektivität der zusätzlichen Opioidwirkung rückschließen.Material und Methode103 Kopfhälften wurden untersucht, die Faszie von lateral her aufgesucht. Dabei unterschieden wir 3 Gruppen: Gruppexa0A repräsentierte vollständig ausgebildete Faszienblätter, Gruppe Bxa0unvollständige Faszien und in Gruppexa0C war die Faszie nicht ausgebildet.ErgebnisDie Faszie war in 86 vollständig und in 13 Fällen unvollständig ausgebildet. Lediglich in 4 Fällen fehlte sie vollends.SchlussfolgerungDie Faszie kann die Erfolgsquote der Schmerzreduktion bei Trigeminusneuralgie beeinflussen.AbstractBackgroundThe almost unknown stylopharyngeal fascia may be one of the reasons for unsuccessful therapy of the trigeminal neuralgia by a transoral block of the superior ganglion of the sympathetic trunk. We investigated the anatomy of the fascia to show the efficiency of the block for this therapy.Materials and methods103 halves of human heads were investigated. The stylopharyngeal fascia was dissected by a lateral approach. We classified three groups. Groupxa0A was formed by fascias without perforation, groupxa0B by perforated fascias and groupxa0C by all halves without a developed fascia.ResultsWe found a fully developed fascia in 86 cases. 13 halves had perforated fascias; in 4 cases the fascia was not developed.ConclusionThe stylopharyngeal fascia may inhibit the distribution of opoids into the infratemporal fossa associated with a consecutive block of the mandibular nerve and lower the rate of pain relief.