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Biomedical subjects

V V Dolenc

Publications and source records attributed to V V Dolenc.

At least 19 recordsLinked to original sources
PubMed2000

Electrical thresholds for biomechanical response in the ankle to direct stimulation of spinal roots L4, L5, and S1. Implications for intraoperative pedicle screw testing.

STUDY DESIGN: A comparison of electrical thresholds for biomechanical response in the ankle and for evoked electromyographic signals from specific leg muscles during intraoperative extradural direct stimulation of roots L4, L5, and S1. OBJECTIVE: To determine whether a biomechanical response in the ankle to direct root stimulation occurs before evoked electromyographic signals and to determine differences in electrical excitability of the roots circumferentially. SUMMARY OF BACKGROUND DATA: Stimulus intensities of 1.2-5.7 mA are reported to evoke electromyographic response in corresponding muscles to direct stimulation of normal roots. Stimulus intensities of 6-8 mA were suggested to detect bony pedicular compromise by stimulation of a hole or a screw during pedicle instrumentation. Electrical thresholds of three-dimensional torque response in the ankle to direct root stimulation have not yet been evaluated and compared with thresholds of evoked electromyogram. METHODS: Direct monopolar stimulation of the surgically exposed roots L4, L5, and S1 was performed from different sites around the root by a cuff multielectrode. Biomechanical response was measured as an isometric torque in the ankle at each of three orthogonal axes. Compound muscle action potentials (CMAPs) from root-specific muscles were detected by a pair of surface or wire electrodes. RESULTS: Mean threshold for biomechanical response in the ankle to stimulation of roots L4, L5, and S1 was 0.72 +/- 0.39 mA and for CMAP response was 1.09 mA +/- 0.36 (N = 13). Thresholds for biomechanical responses were significantly lower than for CMAP responses (P = 0.0004; paired t test). Nerve roots were electrically most excitable on their ventral aspects. CONCLUSION: The biomechanical response in the joint to root stimulation can be used to test all root-related muscles crossing that joint at their individual innervation pattern and their residual innervation and to detect electrical excitation of the root at electric thresholds lower than those for detecting CMAP from single standard root-specific muscle. However, this method does not provide sufficient root specificity. It will be valuable in conjunction with multimodality neurophysiologic monitoring of the roots for earlier and more reliable detection of pedicle bone breakthrough or integrity. Further clinical investigations are suggested.

Ankle↗
PubMed2000

Motor response of the leg muscles produced by position-selective stimulation of spinal nerve roots.

OBJECTIVE: To define and measure motor responses of the leg muscles in the ankle associated with position-selective and tetanic stimulation of spinal nerve roots L3-S1. METHODS: Sixteen lumbosacral spinal nerve roots in 14 subjects were stimulated intraoperatively after surgical exposure and decompression for a herniated disc. Each contact of a spiral cuff multielectrode was wrapped around the root and used to excite a spatially defined population of axons beneath the electrode. The motor response from each stimulated position was evaluated in terms of three-dimensional vector torque in the ankle. RESULTS: Each position at which the stimulating electrode was placed around the root exhibited the same vector torque qualitatively, but at different thresholds. The root was most excitable ventrally. The S1 roots responded with a uniform three-dimensional torque pattern: plantar flexion plus lateral leg and foot rotation plus inversion. All L5 roots responded by plantar flexion. Dorsiflexion torque was possible only with stimulation of the L3 and L4 roots. Eversion was not possible with stimulation of the S1 roots or with most of the L5 roots. CONCLUSION: Position-selective stimulation of the extrathecal spinal nerve roots influences the threshold of the biomechanical response, the torque recruitment dynamics, and the magnitude of three-dimensional vector torque. Selective activation of some leg muscles or agonist muscle groups with stimulation of a single nerve root could not be achieved owing to the low spatial selectivity of the stimulation design and/or the low muscle specificity of motor fascicles in the root. Direct extrathecal stimulation of spinal nerve roots has some hypothetical advantages over stimulation of other sites along the peripheral nerves, owing to their unique anatomy, and may contribute to functional electrical stimulation of the lower extremities. Further investigation with a more selective multielectrode configuration and the use of multiple root stimulation is suggested.

Adult↗
PubMed1999

Laterocavernous sinus.

Here we describe an anatomic structure that takes the form of a venous channel (VC) within the two layers of the lateral wall of the cavernous sinus (CS). Colored gelatin was injected in both superficial middle cerebral veins (SMCV) of 29 human specimens. When a SMCV terminated into the CS, the latter was dissected giving particular attention to its lateral wall. The termination of the VC and its eventual communications with the CS and adjacent venous structures were studied. A VC in the lateral wall of the CS was found in 14 of 58 lateral walls (24.1%). It was in continuation with the SMCV in 13 cases, with the uncal vein in one case. The VC drained into the superior petrosal sinus (71.4%), the pterygoid plexus (21.4%), or the posterior part of the CS (7.2%). Two alternate drainage pathways for the SMCV were observed, toward the anterosuperior aspect of the CS (13.8%) or through a paracavernous sinus located along the floor of the middle cranial fossa (32.8%). These different pathways were not observed to occur concomitantly. SMCV were absent in 29.3%. Despite its close topographic relation with the CS, the VC in the lateral wall can be considered as an anatomic entity with potential clinical relevance. We propose to call it the laterocavernous sinus.

Adult↗
PubMed1999

A combined transorbital-transclinoid and transsylvian approach to carotid-ophthalmic aneurysms without retraction of the brain.

A series of 138 patients with 143 carotid-ophthalmic aneurysms (COAs) have been treated by direct surgical approach over the past 15 years. In 5 cases the COAs were bilateral and in 15 cases either one or more aneurysms were associated with a COA. Of the 143 COAs, 87 were small, 41 large and 15 were giant. Seventy-four COAs bled, while 69 were diagnosed either incidentally or else manifested themselves through neurological deficits resulting from compression of the adjacent structures by the aneurysms. Visual deficits were diagnosed in all the patients with large/giant COAs and in 27 patients with small COAs. Of the whole series of patients operated on for COAs, 2 died after surgery. Two patients had endocrinological deficits, 2 had hemiparesis, 36 had the same visual deficits as prior to surgery, whereas in 47 patients the visual function improved. Of all the 138 patients, 96 remained without neurological deficits, and the 36 patients with the same visual deficits as preoperatively also showed no neurological deficits after surgery and hence they were able to resume their previous way of life. Vasospasm did not occur in patients with COA(s) only, but was observed in 6 out of 15 patients with multiple aneurysms where subarachnoid hemorrhage (SAH) had occurred due to a rupture of an aneurysm other than the COA. There has been a major change in the surgical approach to COAs, from the classical pterional intradural approach to the transorbital-transclinoid and transsylvian approach which is described in this report. The latter approach provides ample space for proximal and distal control of the internal carotid artery (ICA) and makes it possible to deal with demanding large/giant COAs safely. In the series presented, there was no case of premature rupture of the aneurysm. Moreover, since we started using the described approach to COAs, retraction of the brain has not been necessary, regardless of the size of the aneurysm.

Aneurysm↗
PubMed1999

Extradural approach to intracavernous ICA aneurysms.

A series of 115 intracavernous internal carotid artery (ICA) aneurysms have been treated by a direct surgical approach during the past 15 years. Sixty-eight aneurysms were small. Of these 11 were traumatic; nine caused by severe head injury and 2 by ICA injury during transsphenoidal surgery. Twenty-six aneurysms were large and 21 were giant. Thirty-eight aneurysms were clipped, 46 were treated by resection followed by ICA wall reconstruction with interrupted sutures, 16 by excision and proximal/distal ICA end-to-end anastomosis and 15 by resection/grafting. Postoperative angiography was performed in 107 cases and the ICA was found to be patent in 100 of these. Three patients died after surgery, two (with traumatic aneurysms) from associated brain injury and 1 from pulmonary embolism. Oculomotor palsy was present in the immediate postoperative period in 104 patients. However, six months after surgery only 7 patients had residual palsy. The direct surgical approach to intracavernous ICA aneurysms has constantly been changed and improved. The approach in its original version [6] was mainly intradural, whereas its contemporary version in most cases is extradural [10, 11]. The latter approach provides complete exposure of the entire parasellar region, good proximal control of the ICA [13], and good access to the cavernous sinus through the individual "corridors" between the cranial nerves [7]. In the author's opinion the direct surgical approach provides better results than endovascular treatment with regard to patency of the ICA [11].

Anastomosis, Surgical↗
PubMed1999

Invasion of the internal carotid artery by cavernous sinus meningiomas.

BACKGROUND: Meningiomas are the most common tumor involving the cavernous sinus. Although these tumors have been known to invade adjacent structures such as bone, soft tissue, and brain, invasion of the internal carotid artery (ICA) by meningiomas has only been recognized recently. The authors evaluate the extent of carotid wall involvement in nine patients with cavernous sinus meningiomas encasing the ICA who underwent en bloc resection of the cavernous sinus. METHODS: The en bloc tumor-ICA specimens were fixed in formalin, embedded in paraffin, and sectioned on a rotary microtome. Hematoxylin and eosin, EVG, and HVG stains were performed and evaluated by light microscopy. RESULTS: There were four males and five females with a mean age of 47 years. Eight patients had not undergone previous surgery, whereas one patient had been operated on before. In this latter case, however, the cavernous sinus was not entered during the first operation. In all patients, stenosis of the ICA was confirmed by preoperative angiography and/or magnetic resonance imaging (MRI). In seven cases, the tumors were excised en bloc along with the stenotic ICA segment. A petrous-to-supraclinoid ICA bypass was performed in these seven patients. In two cases, the tumor was excised with the stenotic artery, but no bypass was performed. The final pathological diagnosis was meningothelial meningioma. In all cases tumor cells were found in the adventitia of the cavernous carotid with stenosis of the arterial lumen. Compression and/or obliteration of the vasa vasorum within the adventia was noted in all specimens. In four cases, the tumor was found to have invaded the external elastic lamina. In two instances the external elastic lamina was disrupted and the tumor focally extended into the media. CONCLUSIONS: These findings suggest that in the case of cavernous sinus meningiomas with encasement and stenosis of the intracavernous ICA, invasion of the vessel wall has occurred. The effect of these findings on the management of cavernous sinus meningiomas and the involved ICA is discussed.

Adult↗
PubMed1999

Traumatic aneurysm and carotid-cavernous fistula following transsphenoidal approach to a pituitary adenoma: treatment by transcranial operation.

A 39-year old woman presented with galactorrhoea. Magnetic resonance imaging revealed an intrasellar tumour. During transsphenoidal surgery to remove the tumour, arterial bleeding occurred from the right internal carotid artery (ICA). The bleeding was stopped by packing with Surgicel. The operation was discontinued at this point and the intrasellar tumour was not removed. Four-vessel angiography was performed on the third day after the operation, revealing a traumatic (false) ICA aneurysm and a low-flow carotid-cavernous fistula (CCF) on the right side. The patient did not have any neurological deficit, and was re-operated on transcranially. Both the traumatic ICA aneurysm and the CCF were excluded from the circulation by a Sundt-Kees cuff clip. The patency of the ICA was preserved.

Adenoma↗
PubMed1999

Biomechanical response in the ankle to stimulation of lumbosacral nerve roots with spiral cuff multielectrode--preliminary study.

Biomechanical response in the ankle to tetanic stimulation of the lumbosacral root was investigated to assess the potential for lower limb functional neurostimulation. Myotomal response in the leg was measured as the three-dimensional isometric torque in the ankle after extradural tetanic stimulation of the L3-S1 roots exposed surgically for herniated disc removal in five patients. The cuff multielectrode was employed to investigate functional topography of the roots by monopolar, bipolar, and tripolar electrode configurations. Four response patterns in the direction of three-dimensional torque vectors were observed. The L-5 and S-1 roots had the same response pattern, but S-1 roots produced stronger torques. Dorsiflexion torque was not obtained by stimulation of L-5 roots despite coactivation of the tibial anterior and peroneal muscles. Dorsiflexion torques were produced only by stimulating the L-4 roots. More selective bipolar and tripolar stimulations recruited force at higher thresholds and less gain. Additionally, some muscles were not activated by tripolar stimulation of the same root. In one L-4 root, the torque at lower electrical threshold was replaced by inverse torque at higher threshold, providing indirect evidence that different muscles may have motoneuron populations that differ in diameter or location within the root. Although dorsiflexion and plantarflexion torques are functional per se, they are accompanied by foot inversion and leg rotation torques (as well as proximal muscle contractions). Further experimental investigations on direct extradural stimulation of lumbosacral roots, either single or in combination, are recommended to explore the potential of lumbosacral nerve root stimulation for restoration of leg function.

Ankle↗
PubMed1999

En bloc resection of an intracavernous oculomotor nerve schwannoma and grafting of the oculomotor nerve with sural nerve. Case report and review of the literature.

A case in which a left oculomotor nerve schwannoma treated by en bloc resection of the lesion and grafting of the oculomotor nerve with sural nerve is presented. Recovery of nerve function was partial, but useful and cosmetically good. The last follow-up examination performed 2 years after surgery revealed recovery of function in the elevator muscle of the upper eyelid, together with slight vertical movement of the eye.

Cavernous Sinus↗
PubMed1998

Anterior communicating artery aneurysm associated with tuberculum sellae meningioma--case report.

A 50-year-old male presented with a very unusual case of a calcified anterior communicating artery (AComA) aneurysm associated with a tuberculum sellae meningioma. Until 10 years previously, the patient had been a professional soccer player for 15 years. He noticed a slight decrease in visual acuity in the right eye 7 years before. The patient was in the care of an oculist throughout this period. Two months before admission, a significant and rapid decrease of vision in the right eye occurred. Computed tomography and magnetic resonance imaging showed a round-shaped, partially calcified tumorous lesion. Four-vessel angiography revealed a large AComA aneurysm. During surgery, a tuberculum sellae. meningioma was found in combination with an AComA aneurysm with a completely calcified wall. The meningioma was resected totally. The AComA aneurysm with a calcified wall could not be clipped or resected and was left alone. His visual deficit improved postoperatively.

Cerebral Angiography↗
PubMed1997

Transcranial epidural approach to pituitary tumors extending beyond the sella.

OBJECTIVE: The treatment of residual and/or recurrent pituitary tumors, initially operated on through transsphenoidal and/or transcranial approaches, required a new single approach that would make it possible to excise the tumor from the sella and from the neighboring regions. Surgical complications, such as pneumatocephalus, cerebrospinal fluid leak, mechanical lesion of the internal carotid artery and/or visual apparatus, and failure to remove the tumor completely, supported the need for an approach that would guarantee a much higher rate of completeness of resection of tumours and also avoid the risk of occurrence of complications. This report does not address endocrinological disorders before surgical treatment of pituitary tumors nor is its aim to present the functional efficacy of surgical treatment relating to hormones. METHODS: The anatomic relationships of the sellar and parasellar regions were studied using central cranial base specimens. Previous anatomic studies of the triangles of the lateral wall of the cavernous sinus (including anteromedial, paramedial, and Parkinson's triangles) and practical experience dealing with tumors in the region led to the use of the triangular windows as key access to the pituitary tumors in the enlarged sella and in the neighboring area(s). RESULTS: During the past 15 years, 210 patients with pituitary tumors extending into the parasellar and other regions beyond the sella were operated on using the transcranial approach. In Group I (consisting of 120 patients), complete removal was achieved in 66.5% of the patients by using the classical approach. Postoperative cerebrospinal fluid leak occurred in 8% and impairment of the visual function in 6% of the patients. With the new approach being used during the last 5 years in Group II (consisting of 90 patients), postoperative impairment of the visual function occurred in only 1 patient and cerebrospinal fluid leak occurred in only 1 other patient. Complete excision was achieved in 92.5% of the patients in Group II. Postoperative improvement of the visual function(s) was achieved for 26% of the patients in Group I and 525 of the patients in Group II. There was no mortality in either the first or the second group. CONCLUSION: The results led to the conclusion that the new approach to pituitary tumors extending beyond the sella (regarding the rate of completeness of the tumor resection) is superior to the previous transcranial approach. Using the new approach, the risks of surgical complications can be avoided by preserving, intact, the diaphragm sellae and the dura covering the central cranial base around the sella.

Adolescent↗
PubMed1996

Cystic trochlear nerve neurinoma.

A case of a cystic neurinoma of the trochlear nerve, originally interpreted as an intrinsic brainstem lesion, is presented. The history of the disease, its clinical picture and surgical treatment are described in detail.

Aged↗
PubMed1994

Frontotemporal epidural approach to trigeminal neurinomas.

From 1980 through 1993 a series of 44 patients with trigeminal neurinomas was treated. Five of them were operated on for the remainder of the tumour as they had undergone previous surgery elsewhere, 35 were operated on for the first time, and 4 were not operated on for various reasons. An epidural approach to the neurinomas originating in the branches of the Vth nerve peripherally to the Gasserian ganglion (GG) was used. In the neurinomas originating in the GG or in the root of the Vth nerve, either an epidural-transdural approach or an epidural-transdural-transpetrous approach was used. All tumours operated on using the approach described in this article were completely removed. In 10 patients, the Vth nerve sensory deficits increased in comparison with preoperative deficits; in 9 their state remained unaltered; and in 11 the sensory function of the Vth nerve improved. In those patients who had experienced pre-operative atypical trigeminal pain, the pain disappeared after surgery. There was no additional treatment: radiosurgery, irradiation or chemotherapy. Histopathological examination did not reveal any malignant changes in the tumours in any of the patients. Based on our own experience and on the published data it is believed that the best treatment for trigeminal neurinomas is complete microsurgical removal of the lesion.

Adolescent↗
PubMed1993

Incomplete spinal cord evoked injury potential in man.

Intraoperative monitoring of spinal cord evoked potentials (SCEP) evoked by tibial nerve stimulation was performed in six patients who underwent junctional coagulation lesion of the dorsal root entry zone for relief of intractable pain. The pain was secondary to complete brachial plexus avulsion. Normal spinal cord evoked potentials showed an initial positive wave and two negative waves, then a group of high frequency conducted waves. On the avulsion side, incomplete spinal cord evoked injury potentials were recorded in all cases and in one on the normal side also. The incomplete spinal cord evoked injury potential consisted of a high-amplitude positive wave with a sharp rising phase and slower falling phase that led to a long lasting, low-amplitude, negative deflection. Several high-frequency components were superimposed onto the monophasic positive wave. The duration of these superimposed components was approximately the same as the duration of the normal spinal cord evoked potentials, but the incomplete spinal cord evoked injury potentials were longer than normal spinal cord evoked potentials for the negative afterwave. Incomplete spinal cord evoked injury potential amplitude was 3-11 times higher than the normal spinal cord evoked potentials. Our results suggest two possible sources of incomplete spinal cord evoked injury potential: the chronic subclinical spinal cord injury produced by the avulsion and the effect of subpial placement of the recording electrodes.

Adult↗