The relationship between nervus intermedius anatomy, ultrastructure, electrophysiology, and clinical function. Usefulness in cerebellopontine microsurgery

BACKGROUND

Although previous studies have described the clinical features of the nervus intermedius (NI), no attempt has yet been made to describe the relationship between the ultrastructural and electrophysiological characteristics of the nervus intermedius and its motor competence.

OBJECTIVE

In this study, we analyzed the intraoperative electrophysiological response obtained during vestibular schwannoma surgery. The ultrastructure was studied using electron microscopy.

MATERIALS AND METHODS

Thirty-six consecutive patients underwent microsurgery for vestibular schwannoma with cerebellopontine angle tumors. The patients were extensively monitored intraoperatively. Selective stimulation of the nervus intermedius was attempted in all cases. The patients were then examined postoperatively and followed for a minimum of 1 year. Forty-three isolated human brainstems were analyzed to collect the ultrastructural NI data.

RESULTS

We found a correlation between the NI motor responses in the perinasal and perioral regions and the ultrastructure characteristics, with few (0.5 %) but large myelinated motor fibers (diameters >12 μm). Both characteristics are consistent with the clinical observation of transient weakness of the levator anguli oris muscle. These observations indicate a relationship between the intraoperative electrophysiological identification of the NI nervus intermedius and its clinical and ultrastructural characteristics.

CONCLUSIONS

Identifying the NI in the deformed anatomy of tumors could provide a fixed landmark during cerebellopontine surgery and help prevent damage of the facial nerve.

Treatment of aneurysmal subarachnoid haemorrhage in Germany: a nationwide analysis of the years 2005-2009

BACKGROUND

The aim of this study was to provide population-based nationwide rates of the different treatment modalities of aneurysmal subarachnoid haemorrhage (aSAH).

METHODS

German Diagnosis-Related Group data of the years 2005-2009 were used to calculate hospitalisation rates for intracranial aneurysm with aSAH. This study includes over 83 million hospitalisations.

RESULTS

We identified 15,768 hospitalisations with a diagnosis of aSAH. Throughout the observation period, the age-standardised rate for both sexes increased by 69% (95% confidence interval, CI 54-84) for coiling and 13% (95% CI 4-23) for clipping. The estimated annual percent change in the overall hospitalisation rate was 7.4% (95% CI 5.2-9.6). Age-standardised hospitalisation rates varied considerably by region. The estimated hospitalisation rate ratio of overall hospitalisation rates (East/West) was 0.86 (95% CI 0.80-0.91) for males and 0.81 (95% CI 0.77-0.85) for females. After adjustment for age and co-morbidity, the hazard ratio (HR) for in-hospital mortality was higher for coiling than clipping (HR = 1.12, 95% CI 1.01-1.23). Patients who received coiling or clipping had ventricular shunt placement in 5.0 (n = 819) and 6.1% (n = 998), respectively. The estimated length of stay was 3.3 days (95% CI 2.56-4.05) shorter for coiling than clipping.

CONCLUSIONS

We provide for the first time nationwide, representative hospitalisation rates for the treatment of aSAH. Our results indicate a change in the practice pattern for Germany during the observation period. We observed a gradual increase in overall hospitalisation rates for aSAH.

A-trains for intraoperative monitoring in patients with recurrent vestibular schwannoma

BACKGROUND

Second surgery of recurrent vestibular schwannoma (VS) after previous surgery, stereotactic radiosurgery (SR) or fractionated radiotherapy (FR) carries an increased risk for deterioration of facial nerve function, e.g., due to adhesions, underlining the need for intraoperative monitoring. Facial “Atrain” EMG activity (“traintime”) correlates with the degree of postoperative facial palsy. Studies investigating A-trains in VS patients with previous surgery, SR or FR are missing. We therefore investigated the value of A-train monitoring in patients undergoing second surgery for VS.

METHOD

Intraoperative EMG data from patients who underwent second surgery for VS after previous surgery, SR and/or FR at our institution between 2006 and 2012 were retrospectively analyzed. Ten patients were selected (5 male): Seven had previous SR/RT and MS, three previous surgery only. Traintime values and distribution was compared to published thresholds and to 77 patients who underwent first surgery for VS during the same time period.

RESULTS

A-trains were recorded early after opening of the dura, before facial nerve preparation. Mean traintime was 46.9 s (18.51 s – 80.82 s) in patients with previous SR/RT. In patients with previous MS only, traintime was 0.06 s, 0.99 s and 22.46 s. Compared to the literature, traintime was higher than expected in six patients (four with previous SR/RT, two without), respectively seven compared to the 77 patients with first surgery (5 SR/RT). Seven patients with previous SR/RT and none with previous surgery showed diffuse A-train distributions without significant percentages in single channels, compared to 60 of 77 patients with first surgery (p <0.02).

CONCLUSIONS

Especially SR/RT, but also previous surgery seems to induce changes in the facial nerve leading to hyperexcitability and exceedingly high traintime values. Based on these findings, A-train monitoring in this specific patient group should be interpreted with caution.

Neuroprotective efficacy of prophylactic enteral and parenteral nimodipine treatment in vestibular schwannoma surgery: a comparative study

BACKGROUND AND STUDY AIMS/OBJECT: Oral nimodipine improves neurologic outcome after aneurysmal subarachnoid hemorrhage. In addition, the neuroprotective efficacy of nimodipine has been revealed following skull base, laryngeal, and maxillofacial surgery. Pharmacokinetic investigations showed nimodipine to reach higher serum levels following parenteral versus enteral administration. Furthermore, a correlation between nimodipine levels in serum, cerebrospinal fluid, and nerve tissue could be quantified. These observations raise the question whether the proven neuroprotective effect of nimodipine is related to its serum level.

PATIENTS/MATERIAL AND METHODS

A consecutive series of 37 patients with vestibular schwannoma treated with nimodipine from the day before surgery until the seventh postoperative day was analyzed retrospectively. Both groups received standard dosages for enteral (n = 17) and parenteral (n = 20) nimodipine medication. Nimodipine levels were measured in pre- and postoperative serum and cerebrospinal fluid samples. Cochlear and facial nerve functions were documented before surgery, in the early postoperative course, and 1 year after surgery.

RESULTS

Facial nerve outcome was significantly better in the group with parenteral nimodipine medication (p = 0.038). Logistical regression analysis revealed a seven times smaller risk for a deterioration of facial nerve function in the group with parenteral treatment. There was no difference in hearing preservation between both groups despite tumor size tending to be larger in the parenteral group. Intraoperative (p = 0.004), postoperative (p = 0.001), and serum and cerebrospinal fluid (p = 0.024) nimodipine levels were significantly higher following parenteral administration as compared with enteral administration. Both groups were comparable regarding tumor size and extent of resection.

CONCLUSIONS

These results support a dependency of nimodipine's neuroprotective efficacy on its serum levels. Parenteral nimodipine treatment produces higher serum levels and has a higher neuroprotective potency in vestibular schwannoma surgery compared with enteral treatment.

D-dimer plasma level: a reliable marker for venous thromboembolism after elective craniotomy

OBJECT

The incidence of deep venous thrombosis (DVT) after craniotomy is reported to be as high as 50%. In outpatients, D-dimer levels of more than 0.5 mg/L indicate venous thromboembolism (VTE, which subsumes DVT and pulmonary embolism [PE]) with a sensitivity of 99.4% and a specificity of 38.2%. However, D-dimer levels are believed to be unreliable in postoperative patients. The authors undertook the present study to test the hypothesis that D-dimer levels would be systematically raised in a postoperative population and to define a feasible threshold for identification of VTE.

METHODS

Doppler ultrasonography of the lower extremity was performed pre- and postoperatively to evaluate for DVT in 101 patients who underwent elective craniotomy. D-dimer levels were assessed preoperatively and on the 3rd, 7th, and 10th days after surgery. Statistical analysis was carried out to define a feasible threshold for D-dimer levels.

RESULTS

D-dimer plasma levels were found to be systematically raised postoperatively, and they differed between patients with and without VTE in a highly significant way. On the 3rd day after surgery, D-dimer levels of more than 2 mg/L indicated VTE with a sensitivity of 95.3% and a specificity of 74.1%, allowing for the definition of a feasible threshold. D-dimer levels of more than 4 mg/L were observed in all patients who had PE during the postoperative period (n = 9). Ventilation time and duration of surgery were identified as highly significant risk factors for the development of VTE.

CONCLUSIONS

Using a threshold of 2 mg/L, D-dimer levels will indicate VTE with a high degree of sensitivity and specificity in patients who have undergone craniotomy. Pulmonary embolism seems to be indicated by even higher D-dimer levels. Given that the development of D-dimer plasma levels in the postoperative period follows a principle that can be predicted and that deviations from it indicate VTE, this principle might be applicable to other types of surgery.

Enteral or parenteral nimodipine treatment: a comparative pharmacokinetic study

BACKGROUND AND STUDY AIMS/OBJECT: Oral nimodipine is recommended to reduce poor outcome related to aneurysmal subarachnoid hemorrhage (SAH). In addition, animal experiments and clinical trails revealed a beneficial effect of enteral and parenteral nimodipine for the regeneration of cranial nerves following skull base, laryngeal, and maxillofacial surgery. Despite these findings there is a lack of pharmacokinetic data in the literature, especially concerning its distribution in nerve tissue.

PATIENTS/MATERIAL AND METHODS

Samples were taken from a consecutive series of 57 patients suffering from skull base lesions and treated with nimodipine prophylaxis from the day before surgery until the seventh postoperative day. Both groups received standard dosages for enteral (n = 25) and parenteral (n = 32) nimodipine . Nimodipine levels were measured in serum, cerebrospinal fluid (CSF), and tissue samples, including vestibular nerves.

RESULTS

Nimodipine levels were significantly higher following parenteral as compared with enteral administration for intraoperative serum (p < 0.001), intraoperative CSF (p < 0.001), tumor tissues (p = 0.01), and postoperative serum (p < 0.001). In addition, nimodipine was significantly more frequently detected in nerve tissue following parenteral administration (Fisher's exact test, p = 0.015).

CONCLUSIONS

From a pharmacokinetic point of view, parenteral nimodipine medication leads to higher levels in serum and CSF. Furthermore, traces are more frequently found in nerve tissue following parenteral as compared with enteral nimodipine administration, at least in the early course.

Erectile dysfunction as rare side effect in the simultaneous intrathecal application of morphine and clonidine

We report on the case of a 52-year-old man who presented with a history of chronic neuropathic pain treated with intrathecal application of morphine for many years. In spite of significant dose escalation, considerable pain relief had not been achieved. Ziconotide had been tried but not only did it not provide pain relief, but it also caused severe side effects in this patient. A combination of morphine and clonidine was delivered by a programmable pump, slowly increasing the clonidine rate over several weeks. For ease of transition and minimization of hospitalization, which was a special concern to this patient, combining clonidine and morphine was chosen over monotherapy with hydromorphone, with both possibilities being described as equal alternatives in the literature. Considerable pain relief was achieved during week 2 at a clonidine dose of 0.040 mg/d, thereby decreasing the visual analog score (VAS) from 10 to 4. Yet, after developing erectile dysfunction and relative hypotension soon after beginning clonidine treatment, the patient decided not to continue with the combined application of morphine and clonidine. Treatment was therefore switched back to the former monotherapy with morphine. Thereafter, erectile dysfunction disappeared and blood pressure returned to habitual high levels. Although common in systemic application, erectile dysfunction caused by the intrathecal application of clonidine has not been described yet in the literature. In this patient, this rare side effect decisively impaired life quality, subjectively outweighing the considerable pain relief which could be achieved after formerly inefficacious treatment. Further and prospective investigation might be needed to estimate the connection of erectile dysfunction to intrathecal application of clonidine.

The nervus intermedius as a variable landmark and critical structure in cerebellopontine angle surgery: an anatomical study and classification

BACKGROUND

An understanding of the normal topography during cerebellopontine angle surgery is necessary to obviate the anatomical distortions caused by tumors.

OBJECTIVE

The aim of this study was to analyze the morphological features of the nervus intermedius (NI) and its related structures in the cerebellopontine angle (CPA).

METHODS

Forty-three isolated human brainstems were examined to collect comprehensive morphometric and topographical data of the NI in its course from the brainstem to the ganglion geniculi, and discover its anatomical relationship with the other neurovascular structures in the CPA as well as within the meatus acusticus internus.

RESULTS

A total of 84 NI were analyzed. The number of bundles comprising the NI varied from one to five. The mean length of the cisternal segment of the NI was 11.47 mm. In most cases, a vein between the root entry/exit zones of the facial and the vestibulocochlear nerve (VN) was documented. In all cases the NI joined the facial nerve, typically (85 %) distally to the the porus within the meatus acusticus internus. The entry/exit zone of the NI can be categorized into four types: in type A, they arise directly from the brainstem; in type B, they arise solely from the facial nerve; in type C solely from the VN; and in type D, where the bundle or bundles arise from both the brainstem and the VN or the facial nerve.

CONCLUSION

The anatomical features of the NI can provide an additional variable landmark and critical structure during cerebellopontine microsurgery. Our study of the nerve's anatomy and topographical relations may contribute to preventing intraoperative nerve injuries.

Prophylactic intravenous nimodipine treatment in skull base surgery: pharmacokinetic aspects

BACKGROUND

Nimodipine is primarily used in subarachnoid hemorrhage (SAH). Clinical trials revealed also a beneficial effect of prophylactic nimodipine treatment on cranial nerve functions following vestibular schwannoma surgery.

OBJECTIVE

The unknown pharmacokinetics of prophylactically administered nimodipine were investigated.

METHODS

Samples were taken from 27 patients with skull base lesions. Prophylactic intravenous nimodipine infusion was started 5.8-25.8 h (mean 17.9 h) before surgery. Nimodipine concentrations were determined in serum (intra- and postoperatively), cerebrospinal fluid (CSF) (intraoperatively), and tissue samples.

RESULTS

Wide interindividual differences were observed. Mean concentrations for nimodipine were 46.9 ng/ml (SD: 6.4; min. 4.1 and max. 92.7 ng/ml) in intraoperative serum, 73.2 ng/ml (SD: 16.7; min. 6.6 and max. 253 ng/ml) in postoperative serum and 8.3 ng/ml (SD: 1.5; min. 1.0 und max. 29.7 ng/ml) in intraoperative CSF. The correlation between intra- and postoperative serum (p=0.004, r=0.560) and between intra-operative serum and CSF concentration (p=0.003, r=0.567) were statistically significant. Furthermore the correlation between intraoperative serum concentration and concentrations collected from vestibular nerves was high (r=0.711), but not statistically significant (p=0.178).

CONCLUSIONS

Interindividually, continously administered intravenous nimodipine produces considerably variable serum levels. Controls of nimodipine serum concentrations may be useful to optimize nimodipine medication in skull base surgery and in the management of SAH. The serum nimodipine level is a useful marker for CSF and intracranial nerve tissue concentrations of nimodipine.

Role of lumbar interspinous distraction on the neural elements

The interspinous distraction devices are used to treat variable pathologies ranging from facet syndrome, diskogenic low back pain, degenerative spinal stenosis, diskopathy, spondylolisthesis, and instability. The insertion of a posterior element with an interspinous device (ISD) is commonly judged responsive to a relative kyphosis of a lumbar segment with a moderate but persistent increase of the spinal canal and of the foraminal width and area, and without influence on low-grade spondylolisthesis. The consequence is the need of shared specific biomechanical concepts to give for each degenerative problem the right indication through a critical analysis of all available experimental and clinical biomechanical data. We reviewed systematically the available clinical and experimental data about kyphosis, enlargement of the spinal canal, distraction of the interspinous distance, increase of the neural foramina, ligamentous structures, load of the posterior annulus, intradiskal pressure, strength of the spinous processes, degeneration of the adjacent segment, complications, and cost-effectiveness of the ISD. The existing literature does not provide actual scientific evidence over the superiority of the ISD strategy, but most of the experimental and clinical data show a challenging potential. These considerations are applicable with different types of ISD with only few differences between the different categories. Despite--or because of--the low invasiveness of the surgical implantation of the ISD, this technique promises to play a major role in the future degenerative lumbar microsurgery. The main indications for ISD remain lumbar spinal stenoses and painful facet arthroses. A clear documented contraindication is the presence of an anterolisthesis. Nevertheless, the existing literature does not provide evidence of superiority of outcome and cost-effectiveness of the ISD strategy over laminectomy or other surgical procedures. At this time, the devices should be used in clinical randomized independent trials in order to obtain more information concerning the most advantageous optimal indication or, in selected cases, to treat tailored indications.

The woman of Pritschoena: an example of the German neolithic neurosurgery in Saxony-Anhalt

We present an outstanding example of successful prehistoric double trephination dating between 2700 and 2200 BC, most likely to the Corded Ware culture, at the end of the Neolithic Age. The particularity of this case is the presence of a double trephination, one frontal over the sinus sagittal superior and one parietal right. There is evidence that the patient survived months to years after the operations. The purpose of the procedure is not known. The case confirms the astonishing degree of technical skills reached in Saxony-Anhalt over 4500 years ago without anesthetic, antiseptic, or technologic aids.

The central myelin-peripheral myelin transitional zone of the nervus intermedius and its implications for microsurgery in the cerebellopontine angle

The central myelin-peripheral myelin transitional zone, also referred to as the "Obersteiner-Redlich zone (ORZ)" or "glial/Schwann junction" of the nervus intermedius, is thought to play a role in the pathophysiology of nervus intermedius neuralgia (NIN). To evaluate the location and histological features of the ORZ of the nervus intermedius (NI), 10 NI specimens from five fresh cadavers were microscopically analyzed for structural differences between their central and peripheral myelin segments. The ORZ was analyzed under a light microscope, and the exact location of the ORZ was confirmed by immunohistochemical staining using an oligodendroglial antibody. The total diameter of the NI showed a mean of 0.62 mm. The cisternal segment of the NI from the brain stem to the porus acusticus internus had a mean length of 13.97 mm. The mean extent of central myelin was 0.5 mm from the brain stem on the medial side and 0.33 mm on the lateral side. Moreover, the mean length of the ORZ was 0.279 mm on the medial side and 0.134 mm on the lateral side. The distance between the brain stem and the most distal point of central myelin that could be detected was 0.67 mm. Accordingly, the ORZ of the NI appears closer to the brain stem compared to the other cranial nerves. The exact location of the ORZ may play a role in diagnostic preoperative imaging, in the planning of surgical procedures for NIN, and may offer suitable landmarks for surgeons performing microvascular decompression in NIN treatment.

Epidermoid tumor of the cerebellopontine angle presenting with selective sudden hearing loss. Intraoperative evidence of a pearl tumor infiltrating and compressing the cochlear nerve

Epidermoid tumors of the cerebellopontine angle are associated with a variety of symptoms, usually attributed to compression and displacement of involved cranial nerves. The authors present a case of a large epidermoid tumor in the left cerebellopontine angle with sudden hearing loss and tinnitus. The intraoperative finding of migration of two tumor pearls into the cochlear nerve was the origin of the clinical sign. The patient improved remarkably after removal of the tumor. This case demonstrates the mechanism for selective hearing loss associated with the large cerebellopontine angle.

Results after treatment of craniopharyngiomas: further experiences with 73 patients since 1997

OBJECT

The authors report surgical and endocrinological results of a series of 73 cases of craniopharyngioma that they treated surgically since 1997 to demonstrate their change in treatment strategy and its effect on outcome compared with a previous series and results reported in the literature.

METHODS

A total of 73 patients underwent surgery for craniopharyngiomas between May 1997 and January 2005. In patients with poor clinical or neuropsychological condition, even following pretreatment, only stereotactic cyst aspiration took place (8 cases). In the remaining patients, gross-total resection (GTR) was intended and appeared to be possible. The most frequent approaches were subfrontal (27 cases) and transsphenoidal (26 cases); in some cases, a multistep approach was used. The rate of GTR, complications, and functional outcome (comparing pre- and postoperative endocrine and neuropsychological testing) were evaluated. The mean duration of follow-up was 25.2 months.

RESULTS

Gross-total resection was achieved in 88.5% of cases in which a transsphenoidal approach was used and 79.5% of those in which a transcranial approach was used (85.2% of those in which a subfrontal approach was used and 72.7% of those in which a frontolateral approach was used). In the total series, GTR was achieved in 83.1% of cases (vs 49.3% in the authors' former series). The complication rate was 13.8% without any mortality. New endocrine deficits were observed more frequently in patients treated with transcranial approaches over the years (16.3%-66.7% vs 2.6%-50.0%) but were less frequent after transsphenoidal approaches (5.2%-19.2% vs 2.9%-45.7%).

CONCLUSIONS

Open surgery with intended total resection remains the treatment of choice in most patients. Initial stereotactic cyst aspiration or medical pretreatment to improve the patients' condition and adequate choice of surgical approach(es) are essential to achieve that goal. Nevertheless, a moderate increase in endocrinological deficits has to be accepted. The authors recommend using radiotherapy only in cases in which there are tumor remnants or disease progression after surgery.