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Biomedical subjects

G Penkert

Publications and source records attributed to G Penkert.

At least 19 recordsLinked to original sources
PubMed2003

[Brachial plexus lesions from the neurosurgical view].

Neurosurgery does not claim to have improved surgery of the brachial plexus. But achievements in microsurgery have advanced surgical possibilities in several faculties. Neurosurgery for example has introduced considerable improvements concerning the assessment of intraforaminal or intraspinal root injuries. Intraoperative inspections of roots via hemi-laminectomy allowed to determine specificity and sensitivity of modern radiological imaging by correlating intraoperative findings with the results of the radiological imaging. Using determined axial MRI with thin sections, we showed root avulsion in a very high quantity. These findings led us to modify our surgical concept. Operations with long exploration were reduced and preoperative planning of neurotisation was improved due to the preoperative diagnostics.

Brachial Plexus↗
PubMed2000

[Potential limitations and risks in the treatment of painful neuropathies].

INTRODUCTION: Neuropathic pains often cause social disintegration of the patients, encouraging us to apply microsurgical techniques to peripheral nerve lesions, but there are limitations and risks to take into account when handling scarred nerve tissue. FACTS AND THEORETICAL CONSIDERATIONS: The historical development of our microanatomical knowledge of grading of nerve lesions as well as facts on different fibrotic intraneural reactions are pointed out and additionally compared to today's theories of the origin of neuropathic pains. METHODS: The microsurgical methods applied to entrapment syndromes, pseudoneuroma and neuroma formations consist of either external and interfascicular neurolysis or nerve grafting depending on the estimated grade of nerve lesion. If we primarily don't try to restore motor function after a nerve lesion but intend to achieve reduction of neuropathic pain due to a scarred nerve, the well-known methods of neuromodulation or thermic/cryoneurotomy increasingly become the treatment of choice. CONCLUSIONS: There is no real mental connection existing between our successful microsurgical methods on restoration of nerve function and the theories of the origin of neuropathic pains. We do treat pain of nociceptive origin by means of neurolysis but have abandoned these methods more and more in the case of chronic neuropathic pain. But on the other hand, the neuromodulation and neurotomy methods preferred in these cases still have limitations in compatibility and success rates. In a few cases we even risk inducing or worsening chronic neuropathic pains by means of microsurgery and/or neurotomy of a lesioned nerve.

English Abstract↗
PubMed2000

In vivo visualization of the neuromuscular junction before and after autologous nerve transfer in the rat.

In vivo visualization of the neuromuscular junction with epifluorescence imaging techniques has become a successful method of observing the ongoing process of re-occupation by regenerating motor axons of former post-synaptic sites after nerve injury. By using a light-integrating video camera for digital documentation, all parts of the neuromuscular junction can be visualized, as detailed as when documented with high-speed film, but with a minimum light intensity to prevent damage of neural or muscular structures. Results from comparisons of pre- and post-synaptic staining indicate a non-reoccupation rate up to 37 percent at a 55-day interval after nerve transfer, and up to 34 percent at a 66-day postoperative interval. Morphologic findings suggest that these high non-reoccupation rates are caused jointly by intramuscular missprouting, an insufficient intramuscular guidance apparatus, and intramuscular microneuroma formation at the insufficient neuromuscular junction.

Animals↗
PubMed1999

Diagnosis and surgery of brachial plexus injuries.

The surgical outcome of traumatic injuries of the brachial plexus (BP) depends on the following parameters: 1) accurate preoperative diagnosis of cervical root avulsion; 2) time interval between injury and surgery; 3) delicate handling of the nerve tissue; and 4) postoperative physiologic training. This report is based on a 15-year experience in brachial plexus surgery and is supported on the grounds of two major studies. In a prospective study, the authors controlled for the reliability of preoperative radiologic diagnosis by myelo-CT and MRI scans for 40 patients, to evaluate the integrity of the intraspinal cervical roots after brachial plexus injury. Surgical inspection via a cervical hemilaminectomy proved the accuracy of 85 percent and 52 percent of CT myelography and MRI, respectively. Retrospective statistical analyses were carried out of the long-term surgical results of 54 patients with traumatic injuries of the BP who received a grafting procedure between cervical roots C5 or C6 and the musculocutaneous nerve. Patients operated on up to 6 months after trauma showed a better result than patients operated on later than 12 months after trauma (p<0.05). In contrast, grafting between cervical root C5 or C6 and the use of different sural-graft sizes to reconstruct the musculocutaneous nerve demonstrated no statistically significant difference in the final outcome.

Analysis of Variance↗
PubMed1997

Diagnosis of root avulsions in traumatic brachial plexus injuries: value of computerized tomography myelography and magnetic resonance imaging.

Surgical management and prognosis of traction injuries of the brachial plexus depend on the accurate diagnosis of root avulsion from the spinal cord. Myelography, computerized tomography (CT) myelography, and recently magnetic resonance (MR) imaging have become the main radiological methods for preoperative diagnosis of cervical root avulsions. Most of the previous studies on the accuracy of CT myelography and MR imaging studies have correlated the radiological findings with the extraspinal surgical findings at brachial plexus surgery. Surgical experience shows that in many cases extraspinal findings diverge from intradural determinations. Consequently, only correlation with the intradural surgical findings will allow assessment of the factual accuracy of CT myelography and MR imaging studies. In a prospective study, 135 cervical roots (C5-8) were evaluated by CT myelography and/or MR imaging and further explored intradurally via a hemilaminectomy. The accuracy of the preoperative CT myelography-based diagnosis in relation to the intraoperative findings was 85%. On the other hand, MR imaging demonstrated an accuracy of only 52%. The most common reasons for false-positive or false-negative findings were: 1) partial rootlet avulsion; 2) intradural fibrosis; and 3) dural cystic lesions. Computerized tomography myelography scans using 1- to 3-mm axial slices prove to be the most reliable method to evaluate preoperatively the presence of complete or partial root avulsion in traumatic brachial plexus injuries. Because extradural judgment of cervical root avulsion can be unreliable, accurate assessment of intraspinal root avulsion enormously simplifies the decision concerning the choice of donor nerves for transplantation and/or neurotization during brachial plexus surgery.

Adolescent↗
PubMed1997

Surgical reconstruction of the musculocutaneous nerve in traumatic brachial plexus injuries.

Over the last 16 years, 345 surgical reconstructions of the brachial plexus were performed using nerve grafting or neurotization techniques in the Neurosurgical Department at the Nordstadt Hospital, Hannover, Germany. Sixty-five patients underwent graft placement between the C-5 and C-6 root and the musculocutaneous nerve to restore the flexion of the arm. A retrospective study was conducted, including statistical evaluation of the following pre- and intraoperative parameters in 54 patients: 1) time interval between injury and surgery; 2) choice of the donor nerve (C-5 or C-6 root); and 3) length of the grafts used for repairs between the C-5 or C-6 root and the musculocutaneous nerve. The postoperative follow-up interval ranged from 9 months to 14.6 years, with a mean +/- standard deviation of 4.4 +/- 3 years. Reinnervation of the biceps muscle was found in 61% of the patients. Comparison of the different preoperative time intervals (1-6 months, 7-12 months, and > 12 months) showed a significantly better outcome in those patients with a preoperative delay of less than 7 months (p < 0.05). Reinnervation of the musculocutaneous nerve was demonstrated in 76% of the patients who underwent surgery within the first 6 months postinjury, in 60% of the patients with a delay of between 6 and 12 months, and in only 25% of the patients who underwent surgery after 12 months. Comparison of the final outcome according to the root (C-5 or C-6) that was used for grafting the musculocutaneous nerve showed no statistical difference. Furthermore, statistical analysis (regression test) of the length of the grafts between the donor (C-5 or C-6 root) nerve and the musculocutaneous nerve displayed an inverse relationship between the graft length and the postoperative outcome. Together, these results provide additional information to enhance the functional outcome of brachial plexus surgery.

Adolescent↗
PubMed1993

[Ganglia of peripheral nerves].

The authors present two different types of ganglion affecting the peripheral nerves: extraneural and intraneural ganglion. Compression of peripheral nerves by articular ganglions is well known. The surgical management involves the complete removal of the lesion with preservation of most nerve fascicles. Intraneural ganglion is an uncommon lesion which affects the nerve diffusely. The nerve fascicles are usually intimately involved between the cysts, making complete removal of all cysts impossible. There is no agreement about the best surgical management to be applied in these cases. Two possibilities are available: opening of the epineural sheath lengthwise and pressing out the lesion; or resection of the affected part of the nerve and performing a nerve reconstruction. While in case of extraneural ganglion the postoperative clinical evolution is very favourable, only long follow up studies will reveal in case of intraneural ganglion the best surgical approach.

Adolescent↗
PubMed1993

[Peripheral nerve injuries--current treatment standard].

A review of our century's efforts to overcome nerve defects reveals the conclusion that today microsurgical techniques and interfascicular nerve grafting offer the best chances to get success in peripheral nerve repair. There exists a theoretical grading system of Sunderland, which enables us to understand the very different factors which might influence the sprouting of nerve fibers within the damaged or repaired nerve segments. But in practice, the indication to operate always depends on our own decision. The neurological status and electrophysiological tests can only sometimes facilitate our treatment and judgement on peripheral nerve lesions. The basic principles of microsurgical nerve repair are still valid. Modern techniques have resulted in better prognosis. Vast mobilization to achieve neurorrhaphy by force is obsolete today. Epineural trunk-to-trunk-suture is only allowed after clean cut-injuries. In all other cases we have to prefer a repair by autologous grafting. But some factors still remain which limits our efforts, such as muscle degeneration depending on time interval or ischemic fibrosis after the lesion, direct trauma to the muscle substance or a lesion in the region of nerve ramifications.

Humans↗
PubMed1991

[An epidural spinal abscess with caudal symptoms as a complication of Crohn's disease].

Progressive symptoms of caudal compression (flaccid paraparesis, sensory disorders), accompanied by severe pain and fever, developed over a few days in a 26-year-old man with Crohn's disease for 11 years. Spinal computed tomography, performed under the diagnosis of herniated disc, revealed intraspinal soft tissue, as well as gas in the spinal canal (L2-S3) and the paravertebral muscles. This led to the diagnosis of acute epidural abscess and a laminectomy was performed (at L4-S2). Intraspinally there was thickened, bluish fatty tissue; thick pus exuded between dura and the sacral roots. Suction-irrigation of the spinal canal was undertaken via an epidural drain. Postoperative contrast infusion into the colon demonstrated a fistula directed towards the sacrum. The postoperative course was complicated by severe respiratory impairment of which the patient died.--Epidural abscess is a rare complication of Crohn's disease. Because of its poor prognosis early diagnosis with magnetic resonance imaging or computed tomography should be undertaken in every patient with Crohn's disease who has back pain, fever or, particularly, symptoms of spinal compression.

Abscess↗
PubMed1991

Vascular lesions of the internal auditory canal.

We report here two cases of vascular tumors arising within the internal auditory canal, both of which presented with cerebellopontine angle symptoms and simulated acoustic neurinomas. The first case was an arteriovenous malformation that caused moderate sensorineural hearing loss, tinnitus, vertigo with lateropulsion, facial weakness, and trigeminal hypoesthesia on the same side. The second case was a venous angioma, to our knowledge the first ever reported in this location, which presented with sudden complete deafness and progressive hemifacial spasm. The latter subsided completely after successful total extirpation of this unique tumor. The literature on these extremely rare lesions is also reviewed.

Journal Article↗
PubMed1989

Surgical treatment of myeloradiculopathy in cervical spondylosis. A report on 438 operations.

In the past eleven years we have performed 438 microsurgical ventral discectomies with bilateral foraminotomy followed by fusion with palacos in the cervical spine in our clinic. An analysis of the preoperative symptoms shows a great variability and overlapping of the various segments. To determine the right level for the operation it is crucial that the results of the clinical and the radiological examinations be evaluated. The results of ascending myelography and CT scans are of great value. In cases of cervical myelopathy a multisegmental operation is often necessary to obtain good results. The complication rate was small in our patients and a second operation was only necessary in a few cases. We had very good postoperative results in radicular pain and muscle weakness. In patients with symptoms of cervical myelopathy we achieved considerable improvement.

Cervical Vertebrae↗
PubMed1988

Revascularization of nerve grafts: an experimental study.

The time course of revascularization of grafted nerves, and the possible dependence of this revascularization on the length of the graft are two related questions that are addressed. Survival of Schwann cells in the nerve graft and a timely revascularization must be seen as a precondition for an optimal regeneration process. The revascularization process after different postoperative intervals is demonstrated in the sciatic nerve of rabbits by the use of microangiography, with Roentgen-positive water-soluble contrast medium. The third postoperative day is the earliest point in time for revascularization of the autologous graft from surrounding tissues. On the fourth postoperative day, a hyperemia with extension to all sides of the intraneural vessel system exists that still persists on the fifth and sixth days. In one experimental group, revascularization was allowed to occur only in a longitudinal direction. Revascularization under these conditions proved to be poor, slow, and obviously dependent on the length of the graft. Survival and subsequent function of free autologous nerve grafts may depend on the diameter of the grafts and the quality of the recipient site, but not on the length of the grafts, when timely revascularization from the surrounding tissues is present.

Animals↗
PubMed1986

[Intermedius neuralgia].

We report 2 cases of microvascular decompression of the nervus intermedius. The current views of aetiology of neuralgia and spasm of the cranial nerves are discussed based on intraoperative observations and electro-optical investigation reported in the literature. The complex anatomy within the sensory system of the facial nerve, and the intersection of its area of supply with that of the glossopharyngeal and vagus nerves are discussed. Surgical treatment is proposed with emphasis on the current preoperative difficulties of interpretation and the intraoperative constant variations in the course of the anterior inferior cerebellar artery.

Arteries↗