Andreas R. Gunkel

Minimally Invasive Head Holder to Improve the Performance of Frameless Stereotactic Surgery

Frameless stereotactic procedures crucially depend on the firmness of immobilization. Once registered, shifting of the patient leads to inaccuracy, and the patient registration has to be realigned. To overcome the drawbacks of conventional invasive fixation for neurosurgery and the widely accepted fixation with surgical tape in ENT, the Vogele‐Bale‐Hohner (VBH) head holder has been developed. It permits rigid, noninvasive fixation of the head by using an individualized dental cast attached to the upper jaw by vacuum. Oral intubation is uncomplicated. In addition, a special registration device providing well defined reference points can be mounted to the mouthpiece. We report the first promising clinical applications of this device.

The hypoglossal-facial anastomosis as model of neuronal plasticity in the rat

Hypoglossal-facial cross anastomosis (HFA) causes regeneration with change of function, as the axotomized hypoglossal motoneurons sprout into the facial plexus and reinnervate the mimic musculature. Following HFA, hypoglossal-hypoglossal single anastomosis (HHA) and resection of 8-10 mm peripheral hypoglossal nerve in 190 female adult Wistar rats, we compared the axon reactions in the hypoglossal nucleus during 1) regeneration with change of function, 2) regeneration with restoration of original function and 3) degeneration of the nucleus. Following postoperative survival times of 1-16 weeks we estimated the volume of the hypoglossal nucleus and counted the number of hypoglossal neurons with the physical disector on both sides of the brainstem. Additional sections of the same animals were reacted with anti-synaptophysin, anti-GFAP and the isolectin Griffonia simplicifolia I-B4 (GSA I-B4) as cytochemical markers for presynaptic boutons, activated astroglia and microglia. After HHA and HFA all hypoglossal neurons survive and the volume of the hypoglossal nucleus remains constant. Resection of the hypoglossal nerve leads to the loss of one third of the hypoglossal neurons and of one third of the volume of the hypoglossal nucleus within 16 weeks post operation. Hypoglossal-facial anastomosis and hypoglossal-hypoglossal anastomosis differ in postoperative swelling of the hypoglossal nucleus, microglia and astroglia activation and the duration of synaptic stripping. All differences are limited to the acute growth phase during regeneration. It is concluded that hypoglossal-facial anastomosis provides more stimulation and facilitates faster recovery of the hypoglossal nucleus than does hypoglossal-hypoglossal anastomosis.

DNA‐fragmentation and expression of apoptosis‐related proteins in experimentally denervated and reinnervated rat facial muscle

Muscle fibres may undergo apoptotic cell death in several neuromuscular disorders such as denervated muscle fibres in spinal muscular atrophies. We investigated DNA‐fragmentation (in situ by the TUNEL‐method) and expression of apoptosis‐associated proteins in experimentally denervated and reinnervated rat facial muscle up to 24 weeks after surgery to evaluate the rate and time lapse of apoptotic muscle fibre loss. While denervated muscle displayed constantly high rates of DNA‐fragmentation, denervated and immediately reinnervated muscle showed a distinct decrease of primarily elevated DNA‐cleavage, finally resembling rates of normal controls. Denervated muscle fibres revealed strong immunoreactivity of the anti‐apoptotic proteins bcl‐2 and bcl‐xL, and the pro‐apoptotic factor bax. In reinnervated muscle fibres, only bcl‐2 was constantly up‐regulated while bcl‐xL and bax diminished after the 7th week. The present findings indicate that denervation may prompt muscle fibres to activate an intrinsic ‘suicide’ programme to undergo apoptosis. High levels of bcl‐2 after denervation may sustain cell survival until reinnervation, e.g. after accidental nerve damage or in neurodegenerative disorders. Furthermore, increasing levels of bcl‐2 are able to neutralize high apoptosis‐promoting bax levels. Interventions modifying DNA‐fragmentation and the expression of apoptosis‐related proteins may lead to new therapeutic concepts in denervating disorders of muscle in the absence of other primary therapies.

Computer‐Aided Surgery in the Petrous Bone

Objectives: We demonstrate that computer‐assisted frameless stereotactic navigation with the ISG/ELEKTA Viewing Wand system in the petrous bone is routinely possible with sufficient application accuracy.

Differences in glial, synaptic and motoneuron responses in the facial nucleus of the rat brainstem following facial nerve resection and nerve suture reanastomosis.

Transection and reanastomosis of the facial nerve with microsurgical sutures in rats (facial-facial anastomosis) results in the complete regeneration of the facial nucleus, whereas resection of a 10 mm length of the peripheral facial nerve leads to degeneration and loss of neurons in the nucleus. Nerve sutures or resections were performed in 84 female Wistar rats, and the time course and differences between regenerative and degenerative reactions in the facial nuclei were compared after survival times of 4–112 days. The volume of the facial nucleus, number of facial motoneurons and motoneuron density were estimated stereologically by the physical dissector method. Synaptic plasticity, activation of astroglia and microglia were studied cytochemically with anti-synaptophysin, anti-glial fibrillary acidic protein and the isolectin Griffonia simplicifolia I-B4 (GSA I-B4). After facial-facial anastomosis the volume of the facial nucleus and its number of motoneurons remained constant, whereas resection of the facial nerve caused shrinkage of the facial nucleus and loss of one-third of facial motoneurons within 112 days post-operation. Synaptic stripping, activation of microglia and astroglia occurred in the same sequence and were reversible after both operations, but these reactions were more severe and prolonged after resection, i.e. without suture of the facial nerve. It appears to be most important clinically that differences between de- and regeneration become clear within 7 days post-axotomy. Our results strongly support reconstruction of the facial nerve as early as possible after a nerve lesion.

Three-Dimensional Image-Guided Endonasal Surgery With a Microdebrider

We report the first intraoperative use of a microdebrider as a stereotactic three‐dimensional (3D) navigation instrument in paranasal and frontobasal surgery. The microdebrider uses rotating blades and an integrated suction device for controlled removal of tissue under video‐endoscopic view. The ISG Viewing Wand uses the patients computed tomography/magnetic resonance (CT/MR) data and a 3D reconstruction thereof and a highprecision position‐sensitive mechanical arm for intraoperative three‐dimensional navigation. We have linked the microdebrider to the Viewing Wand to transform it into a continuously available intraoperative stereotactic localizing device. We discuss the problems related to this extension of the Viewing Wand and demonstrate the practical use in an exemplary polypectomy.

Expression of different isoforms of nitric oxide synthase in experimentally denervated and reinnervated skeletal muscle.

Denervated muscle fibers express enhanced levels of stress and apoptosis-associated proteins and undergo apoptosis. In experimentally denervated and reinnervated rat facial muscle, we now evaluate changes in the expression patterns of different isoforms of nitric oxide synthase (NOS)–generating nitric oxide (NO), which mediates oxidative stress and apoptosis. Physiological expression of NOS corresponds to a constant sarcolemmal staining pattern for neuronal NOS (nNOS) and a patchy sarcolemmal and weak sarcoplasmic labeling for the endothelial NOS-isoform, with no expression for inducible NOS (iNOS). Denervated muscle displayed distinct downregulation of nNOS with preserved expression of dystrophin. Also, denervated and immediately reinnervated muscle fibers showed decreased expression of nNOS. However, muscle fibers rein-nervated for 10 weeks revealed a restored physiological expression of nNOS. There were no changes in the expression of endothelial and inducible NOS. As NO is known to induce growth arrest and collapse of neuronal growth cones, downregulation of NOS may contribute to promotion of axonal regeneration by aiding formation of new endplates. NO is upregulated in reinnervated muscle fibers and thus prevents polyneural hyperinnervation by extrajunctional synapses. Furthermore, downregulation of NOS during denervation is compatible with the finding that low levels of NO contribute to apoptosis instead of necrosis in disease states of oxidative stress.

CHANGES IN EYE BLINK RESPONSES FOLLOWING HYPOGLOSSAL-FACIAL ANASTOMOSIS IN THE CAT: EVIDENCE OF ADULT MAMMAL MOTONEURON UNADAPTABILITY TO NEW MOTOR TASKS

Hypoglossal-facial anastomosis is used in humans to restore the activity of the mimic musculature following irrecoverable facial nerve lesions. As eyelid movement kinetics is very well known, we have used this experimental model in cats to follow the evolution of blink responses and the adaptability of hypoglossal motor pools to new motor tasks. Although the electromyographic activity of the orbicularis oculi muscle in response to corneal air puffs, flashes of light or electrical stimulation of the supraorbital nerve was not recovered in the seven months following this crossed anastomosis, reflex blinks were got back by the increased activity of the retractor bulbi and extraocular recti muscles. The lid of the anastomosed side oscillated in perfect synchronization with tongue movements during licking, while it was severely affected in its motor function during optokinetic stimulation because of the spontaneous appearance of tongue-related hypoglossal activity. Present results suggest that adult mammal motoneurons are unable to readapt their motor programs to the kinetic needs of new motor targets and that most of the functional recovery observed in the cat was achieved by the compensatory hyperactivity of motor systems not directly affected by the surgery.

3D-Navigation in der interstitiellen stereotaktischen Brachytherapie

ZusammenfassungZielEs was das Ziel dieser Arbeit, ein 3D-Infrarotnavigationssystem für die Anforderungen der interstitiellen stereotaktischen Brachytherapie zu adaptieren. Damit wird die Planung der Therapie verbessert (prospektive Planung der Nadelpositionen und der Dosisverteilung), und eine virtuelle Simulation wird realisierbar (Kontrolle des vorgeplanten Zugangs bezüglich Verletzungsmöglichkeit von Gefäßen oder Nerven).Material und MethodeDas EasyGuide-Neuro®-Navigationssystem (Philips) wurde so verändert, daß Nadeln, die in der Brachytherapie Verwendung finden, am Pointer befestigt werden konnten und am Bildschirm angezeigt wurden. Um die Genauigkeit der Positionierung zu bestimmen, wurde versucht, an Phantomen definierte Zielpunkte zu treffen. Dazu wurden zwei unterschiedliche Methoden miteinander verglichen. Einerseits das “freie Navigieren”, eine Applikationsmethode, bei der die Nadel mit Hilfe des Navigationssystems geführt wurde, und andererseits das “Navigieren mit Template”, bei der die Nadel über ein ausgerichtetes Template und das Navigationssystem ins Ziel geführt wurde. Es wurde auch getestet, ob ein Maskensystem die Anforderungen der stabilen und reproduzierbaren Lagerung erfüllt. Die Umsetzbarkeit der neuen Methode in die klinische Praxis wurde anschließend an einem anatomischen Präparat geprüft.Ergebnisse91% aller durchgeführten Versuche mit den Phantomen wiesen eine Abweichung <5 mm auf. Die Versuche auf einem stabileren Tisch lieferten deutlich bessere Ergebnisse (94% <4 mm). Kein Unterschied konnte zwischen den Applikationsmethoden (“freies Navigieren” und “Navigieren mit Template”) festgestellt werden.SchlußfolgerungenDie Genaulgkeit der Phantomversuche und die Versuche mit dem anatomischen Präparat zeigten, daß mit stabilen Tischen und Lagerungssystemen auch im klinischen Einsatz ausgezeichnete Ergebnisse erzielt werden können.AbstractAimThe aim of this paper is to describe the adaption of 3D-navigation for interstitial brachytherapy. The new method leads to prospective and therefore improved planning of the therapy (position of the needle and dose distribution) and to the possibility of a virtual simulation (control if vessels or nerves are on the pathway of the needle).Material and MethodsThe EasyGuide Neuro® navigation system (Philips) was adapted in the way, that needles for interstitial brachytherapy were made connectable to the pointer and correctly displayed on the screen. To determine the positioning accuracy, several attempts were performed to hit defined targets onphantoms. Two methods were used: “free navigation”, where the needle was under control of the navigation system, and the “guided navigation” where an algined template was used additonally to lead the needle to the target. In addition a mask system was tested, whether it met the requirements of stable and reproducible positioning. The potenitial of applying this method in clinical practice was tested with an anatomical specimen.ResultsAbout 91% of all attempts lied within 5 mm. There were even better results on the more rigid table (94% <4 mm). No difference could be seen between both application methods (“free navigation” and “navigation with template”), they showed the same accuracy.ConclusionsThe accuracy of the phantom experiments and the confirmation by the experiment with the anatomical specimen showed that excellent results can be expected in clinical practice using rigid tables and patient supporting systems.

Three-Dimensional Navigation in Otorhinolaryngological Surgery with the Viewing Wand

We report our experiences with the ISG Viewing Wand intraoperative 3-dimensional navigation device in endonasal endoscopic procedures of the paranasal sinuses, anterior skull base, and petrous bone. In the last 12 months we have routinely used the wand in 90 patients for treatment of polyposis nasi, for biopsies and removal of tumors in the nasal cavity and at the frontal skull base, for endocrine ophthalmopathy, and in 1 case for cholesteatoma. We present our computed tomography, magnetic resonance imaging, and clinical protocols that allow a precise routine use of the Viewing Wand. In all cases, the system was extremely helpful for intraoperative localization and helped to optimize surgery.