Vestibular schwannomas: surgical approach.
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Humans↗
Biomedical subjects
M Samii
Publications and source records attributed to M Samii.
Artificial elevation of brain tissue glycerol by administration of a glycerol-containing agent. Case report.
In recent years the development of secondary brain damage and derangement of neurochemical parameters after severe head injury has been monitored using microdialysis. Provided the blood-brain barrier is intact, glycerol is regarded as a potential marker for membrane phospholipid degradation. The authors report a case in which marked elevation of interstitial glycerol was induced after exogenous administration of a glycerol-containing agent. A 25-year-old man was injured in a motorcycle accident and was admitted to the authors' institution with a unilateral dilated and fixed pupil and a Glasgow Coma Scale score of 3. Computerized tomography scans revealed a large subdural hematoma on the left side, subsequent midline shift, and generalized edema. Emergency craniotomy was performed for evacuation of the hematoma. The patient was prepared for multisensory monitoring and a microdialysis catheter was inserted into his left frontal lobe. After a routine enema containing 85% glycerol had been administered, the authors measured a marked increase in glycerol in the dialysate. This occurred while the patient was in as stable a condition as could be expected given the circumstances. The increase in interstitial glycerol in the injured tissue was most likely due to an impaired blood-brain barrier. Thus, the interstitial glycerol concentration had been corrupted by exogenous glycerol, and the marker properties of glycerol in this case became questionable. Consequently, administration of glycerol, which is frequently found in various infusions and emulsions, can promote secondary brain damage by adversely shifting osmotic gradients.
Adult↗
Brachial plexus palsy from nodular fasciitis with spontaneous recovery: implications for surgical management. Case illustration.
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Adult↗
Surgical management of brainstem cavernomas.
OBJECT: A careful retrospective analysis of 36 cases was performed to evaluate the pre- and postoperative rates of morbidity that occur in patients with brainstem cavernous angiomas. METHODS: The authors evaluated immediate postoperative and follow-up outcomes with regard to clinical findings, the incidence of preoperative hemorrhage(s), location and size of the lesions, and the timing of the surgical procedure after the last hemorrhagic event. Specifically. the following parameters were analyzed: 1) number of hemorrhages; 2) the precise brainstem location (pontomesencephalic, pons, and medulla oblongata); 3) pre- and postoperative cranial nerve status; 4) pre- and postoperative motor and sensory deficits; 5) size (volume) of the lesions; and 6) pre- and postoperative Karnofsky Performance Scale (KPS) scores. Multiple hemorrhages were observed in 16 patients, particularly in those with pontomesencephalic cavernous angiomas (75%). The mean preoperative KPS score was 70.3 +/- 16.3 (+/- standard deviation). Twenty-six patients (72.2%) presented with cranial nerve impairment, 13 (36.1%) with motor deficits, and 17 (47.2%) with sensory disturbance. Volume of the lesions ranged from 0.18 to 18.18 cm3 (mean 4.75 cm3). Postoperative complications included new cranial nerve deficits in 17 patients, motor deficits in three, and new sensory disturbances in 12 patients. In a mean follow-up period of 21.5 months, KPS scores were 80 to 100 in 22 patients. Timing of surgery (posthemorrhage) and multiple hemorrhages did not influence the long-term results. Higher preoperative KPS scores and smaller-volume lesions, however, were factors associated with a better final outcome (p < 0.05). Major morbidity was related mainly to preoperative status and less to surgical treatment. The incidence of new postoperative cranial nerve deficits was clearly lower than that demonstrated preoperatively because of the brainstem hemorrhages. CONCLUSIONS: Based on these findings, resection of brainstem cavernomas is the treatment of choice in the majority of these cases because of the high incidence of morbidity related to one or often several brainstem hemorrhages.
Adolescent↗
Far-field responses to stimulation of the cochlear nucleus by microsurgically placed penetrating and surface electrodes in the cat.
OBJECT: A new generation of penetrating electrodes for auditory brainstem implants is on the verge of being introduced into clinical practice. This study was designed to compare electrically evoked auditory brainstem responses (EABRs) to stimulation of the cochlear nucleus (CN) by microsurgically implanted surface electrodes and insertion electrodes (INSELs) with stimulation areas of identical size. METHODS: Via a lateral suboccipital approach, arrays of surface and penetrating microelectrodes with geometric stimulation areas measuring 4,417 microm2 (diameter 75 microm) were placed over and inserted into the CN in 10 adult cats. After recording the auditory brainstem response (ABR) at the mastoid process, the CN, and the level of the inferior colliculus, EABRs to stimulation of the CN were recorded using biphasic, charge-balanced stimuli with phase durations of 80 microsec, 160 microsec, and 240 microsec at a repetition rate of 22.3 Hz. Waveform, threshold, maximum amplitude, and the dynamic range of the responses were compared for surface and penetrating electrodes. The EABR waveforms that appeared for both types of stimulation resembled each other closely. The mean impedance was slightly lower (30 +/- 3.4 kohm compared with 31.7 +/- 4.5 kohm, at 10 kHz), but the mean EABR threshold was significantly higher (51.8 microA compared with 40.5 microA, t = 3.5, p = 0.002) for surface electrode arrays as opposed to penetrating electrode arrays. Due to lower saturation levels of the INSEL array, dynamic ranges were almost identical between the two types of stimulation. Sectioning of the eighth cranial nerve did not abolish EABRs. CONCLUSIONS: Microsurgical insertion of electrodes into the CN complex may be guided and monitored using techniques similar to those applied for implantation of surface electrodes. Lower thresholds and almost equivalent dynamic ranges indicate that a more direct access to secondary auditory neurons is achieved using penetrating electrodes.
Animals↗
Duplicated abducent nerve and its course: microanatomical study and surgery-related considerations.
OBJECT: The anatomy of the abducent nerve is well known; its duplication (ranging from 5 to 28.6%), however, has rarely been reported in the literature. The authors performed a microanatomical study in 100 cadaveric specimens (50 heads) to evaluate the prevalence of this phenomenon and to provide a clear anatomical description of the course and relationships of the nerve. The surgery-related implications of this rare anatomical variant will be highlighted. METHODS: The 50 human cadaveric heads (100 specimens) were embalmed in a 10% formalin solution for 3 weeks. Fifteen of them were injected with colored neoprene latex. A duplicated abducent nerve was found in eight specimens (8%). In two (25%) of these eight specimens the nerve originated at the pontomedullary sulcus as two independent trunks: in one case the superior trunk was thicker than the inferior and in the other it was thinner. In the other six cases (75%) the nerve originated as a single trunk, splitting in two trunks into the cisternal segment: in two of them the trunks ran below the Gruber ligament, whereas in four specimens one trunk ran below and one above it. In all the specimens, the duplicated nerves fused again into the cavernous sinus, just after the posterior genu of the internal carotid artery. CONCLUSIONS: Although the presence of a duplicated abducent nerve is a rare finding, preoperative magnetic resonance imaging should be performed to rule out this possibility, thus tailoring the operation to avoid postoperative deficits.
Abducens Nerve↗
Neurenteric cyst of the craniocervical junction. Report of three cases.
Neurenteric cysts of the craniocervical junction (CCJ) are very rare lesions. Their origin is the subject of long-standing controversy, but a failure during the embryogenic phase may be responsible for their formation. Accurate histopathological diagnosis may be difficult due to the similarity they share with other cystic lesions such as colloidal cysts, Rathke cysts, and cystic teratomas. Surgical removal is the treatment of choice for intracranial neurenteric cysts, but in some cases, infiltration of the surrounding structures may hinder complete resection. Three cases of neurenteric cysts located at the CCJ are reported.
Adult↗
Neurotropin-3 and spinal ganglion neurons.
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Animals↗
Treatment of refractory pain after brachial plexus avulsion with dorsal root entry zone lesions.
OBJECTIVE: Significant numbers of patients experience intractable pain after brachial plexus root avulsions. Medications and surgical procedures such as amputation of the limb are often not successful in pain treatment. METHODS: Forty-seven patients with intractable pain after traumatic cervical root avulsions were treated with dorsal root entry zone coagulation between 1980 and 1998. The dorsal root entry zone coagulation procedure was performed 4 months to 12 years after the trauma, and patients were monitored for up to 18 years (average follow-up period, 14 yr). RESULTS: Immediately after surgery, 75% of patients experienced significant pain reduction; this value was reduced to 63% during long-term follow-up monitoring. Nine patients experienced major complications, including subdural hematomas (n = 2) and motor weakness of the lower limb (n = 7). Improved coagulation electrodes with thermistors that could produce smaller and more-accurate lesion sizes, which were introduced in 1989, significantly reduced the number of complications. CONCLUSION: Central deafferentation pain that persists and becomes intractable among patients with traumatic cervical root avulsions has been difficult to treat in the past. Long-term follow-up monitoring of patients who underwent the dorsal root entry zone coagulation procedure in the cervical cord indicated that long-lasting satisfactory relief is possible for the majority of individuals, with acceptable morbidity rates.
Brachial Plexus↗
1H-MR spectroscopic monitoring of posttraumatic metabolism following controlled cortical impact injury: pilot study.
Proton magnetic resonance spectroscopy (1H-MRS) has been increasingly utilised in experimental traumatic brain injury for characterisation of posttraumatic metabolic dysfunction. Following human brain injury pathological findings correlated with outcome measures. Combined with conventional T2-weighted MR imaging MRS is a sensitive tool to evaluate metabolic changes in brain tissue following trauma. Studies have been restricted so far to diffuse axonal injury models and fluid percussion injury. Using a high resolution scanner at 4.7 T, MRI combined with 1H-MRS was applied in a pilot study to the controlled cortical impact injury model of experimental brain contusion (CCII). Eight Sprague-Dawley rats were investigated, of which two served as controls. Four animals were injured 24 h after craniotomy, two investigated at 72 h post craniotomy. MRS/MRI indicated a transient brain oedema development and metabolic changes induced by the craniotomy itself. Following CCII MRI demonstrated that the area of contusion as well as the surrounding brain oedema increased twofold in size within 24 h (p < 0.05). MRS showed an immediate increase of N-acetylaspartate (NAA) and glutamate ipsilateral to the contusion and a drop of NAA on the contralateral side. MRS/MRI investigations in the CCII model demonstrated a potential to further elucidate the pathophysiology following traumatic brain contusion.
Animals↗
ICP and MABP following traumatic subarachnoid hemorrhage in the rat.
Traumatic subarachnoidal hemorrhage (t-SAH) is a common finding in head-injured patients occurring with a frequency of 39% according to data of the Traumatic Coma Data Bank. The present study is the first description of a t-SAH-model with particular emphasis on patterns of intracranial pressure (ICP) changes and mean arterial blood pressure (MABP) response. Diffuse brain injury was produced in intubated and ventilated adult Sprague-Dawley rats (N = 24) using a brass weight (500 gm) free falling from a predetermined height (1.5 m) on a steel disc glued to the skull of the rat. Before induction of the injury, heparin was administered intra-arterially (i.a.) and antagonised after injury by protamine. MABP-recordings and ICP-recordings were performed continuously. Histopathology was undertaken. Following injury MABP decreased from 138 +/- 14 mmHg to 89 +/- 22 mmHg. During 5 to 15 min ICP increased up to 89.4 +/- 50.4 mmHg, decreasing slowly within 60 min in surviving animals. The mortality rate was 41.6%. All brains showed a severe subarachnoid hemorrhage in the basal cisterns and cell-loss within the brainstem. Experimental t-SAH is possible. Following t-SAH there is a subacute increase of ICP due to the actual bleeding. The model may provide deeper understanding in the basic physiological patterns of t-SAH.
Animals↗
Influences of secondary injury following traumatic brain injury in developing versus adult rats.
Hypoxia and hypotension are both common findings following traumatic brain injury occurring with a frequency of up to 46% according to data of the Traumatic Coma Data Bank. In the present study the influence of secondary injury on intracranial pressure and the cardiovascular response is investigated in developing rats. Differences from adult rats are determined. Diffuse brain injury was produced in intubated and ventilated 17-20 days old Sprague-Dawley rats (N = 16) using a modification of the Marmarou-model. Hypoxia was induced by reducing O2-concentration to 8% lasting for 15/30 min. Mean arterial blood pressure recordings and intracranial pressure recordings were performed continuously. Animals were divided into two groups, sustaining hypoxia alone (N = 9) and trauma/hypoxia (N = 7). The results were compared to readings in adult animals subjected to hypoxia (N = 5) and trauma/hypoxia (N = 5) (450 gm/150 cm). Immediately following the onset of hypoxia in the developing rat, MABP decreased from 76.5 +/- 13 mm Hg to 35.8 +/- 7 mm Hg. In the adult rat the decrease was more marked (from 93.3 +/- 8 mm Hg to 33.5 +/- 5.7 mm Hg) (p < 0.05). Mortality rate in developing rats with trauma/hypoxia was 43% with no significant change of ICP (from 13 +/- 5.2 to 22.3 +/- 11). All adult animals recovered following trauma/hypoxia with no relevant ICP-increase within one hour post-trauma. Hypoxia induces hypotension in adult and developing rats. However, developing rats appear to be more vulnerable to hypoxia associated with trauma.
Age Factors↗
Application of clinically recorded ICP patterns--an extension of conventional shunt testing.
Various methods of laboratory testing are currently being used to explore the hydrodynamic properties of shunts. We constructed a novel shunt-testing rig with a human-like compliance to be able to subject shunts to in-vivo recorded ICP patterns. The human-like situation was realized with a pear-shaped glass container with a non-linear, third-order pressure/volume characteristic similar to the CSF system. The new device also allows conventional shunt testing. Shunt performance in conventional pressure/flow tests (linear compliance) was compared to tests with human-like compliance. No clinically relevant differences were seen. Clinically recorded ICP waves (Lundberg type A and B) were reproduced before and after shunt implementation. Shunt insertion reduced pressure in the A-wave pattern to slightly negative values. Reproducing B-waves, the shunt dampened wave amplitude and pressure decreased below the opening pressure of the valve. In conclusion, the presented device allows a standardized reproduction of ICP patterns. The effects of shunt implantation can be studied.
Cerebrospinal Fluid↗
Acoustic evoked response following transection of the eighth nerve in the rat.
OBJECT: The auditory brainstem response (ABR) is the most widely used means of intra-operative monitoring of the integrity of the auditory nerve and brainstem pathways during surgery in the cerebellopontine angle (CPA). Reliability of this and other electrophysiological techniques has been questioned because of persisting potentials in direct nerve recordings despite complete eighth nerve section. The study was designed to assess the extent to which an acoustic evoked response persists after the cochlear nerve is lesioned in the CPA of the adult rat. METHODS: The eighth nerve was exposed microsurgically via a lateral suboccipital approach without damage to surrounding structures. The auditory brainstem response to monaurally presented click stimuli was recorded using needle electrodes and a bandpass of 10 to 5000 Hz. FINDINGS: Complete sharp sectioning of the nerve in the CPA resulted in immediate disappearance of brainstem-generated potentials but persistence of a large primary, vertex-positive wave in all but one case. This response was also abolished in recordings three days later and after emptying the inner ear canal. Provided that the cochlea remained intact, two weeks later a single, vertex-positive potential in the latency range of wave Ia of the ABR reappeared, reaching its peak amplitude six weeks after sectioning of the nerve. CONCLUSIONS: The short-latency electrical potential recorded following damage of the eighth nerve in the cerebellopontine angle can be mistaken for an indication that nerve function is still preserved. The evoked injury potential is probably the major contributor to this potential that resembles wave I of the ABR. Monitoring of functional auditory integrity must neither be limited to early components of the ABR, nor to the electrocochleogram (EcoG) and the peripheral compound nerve action potential (CNAP), respectively.
Action Potentials↗
Solitary follicular thyroid carcinoma of the skull base and its differentiation from ectopic adenoma--review, use of galectin-3 and report of a new case.
With only four histologically proven cases in the literature, solitary skull base metastasis of thyroid carcinoma is extremely rare. Having treated another patient harboring a lesion with osseous destruction in the petroclival region and downward soft tissue extension we analyzed this case in conjunction with previous reports. In contrast to parenchymal brain metastasis that usually consists of the papillary type, histological examination revealed differentiated follicular tumors in all cases. All were located around the clivus. The radiographic picture resembled that of chordomas or chondrosarcomas. In the tissue obtained during thyroidectomy no evidence of primary malignancy was found in any of the cases according to standard histological criteria. In our case, a recently developed immunocytological marker - galectin-3 - was applied to differentiate between ectopic thyroid adenoma and carcinoma. The results were indicative of anaplastic growth. Tumor remnants responded well to postoperative 131I internal radiation and TSH suppression therapy. Distant metastasis of follicular thyroid carcinoma has to be considered in the differential diagnosis of destructive skull base lesions. Histological evaluation should include immunohistochemistry or clonal analysis to differentiate between adenomatous and carcinomatous growth and initiate effective radiotherapy early. Prognosis is by far not as poor as in brain metastases and appears to depend largely on location, size and histological appearance.
Adenocarcinoma, Follicular↗
De novo formation of an aneurysm in a case of unusual intracranial fibromuscular dysplasia.
Intracranial fibromuscular dysplasia (FMD) is a vascular disease of unknown origin occurring predominantly in young women. The internal carotid artery is most often involved, but other cerebral arteries may also be affected. We report the case of a young woman presenting with an unusual angiographic appearance of intracranial FMD of the internal carotid artery (ICA) that could not be categorized into any type of the Osborn-Anderson classification. During follow up the patient presented with an intracerebral and subarachnoid hemorrhage. Repeated angiography revealed multiple aneurysms in the pathologic segment of the vessel. The patient underwent surgical treatment with clipping of the aneurysms, wrapping of the pathologic segment of the ICA and biopsy of the superficial temporal artery. Histopathological sections revealed FMD of the intimal type. alpha(1)-antitrypsin blood levels were normal. Cases of intracranial FMD previously reported in the literature are reviewed and various aspects of this rare disease are discussed.
Adult↗
Expression of cathepsin K in chordoma.
Invasive growth of chordoma is accompanied by severe destruction of adjacent bone tissue, a fact that requires high proteolytic activity at the tumor invasion fronts. In this context, cathepsin K is a candidate molecule. It is a protease with high collagenolytic and elastinolytic activity and previously thought to be restricted to osteoclasts and osteoclast-mediated bone resorption. In this study, 44 cases of chordoma of sphenooccipital localization, and 10 embryo-fetal specimens including chorda dorsalis were studied immunohistochemically for their expression of cathepsin K. In 4 additional snap-frozen chordoma cases, the enzyme expression was investigated by reverse transcription polymerase chain reaction and enzyme histochemistry. Ten chondrosarcomas of the skull base served as controls. Various concentrations of cathepsin K mRNA could be seen in all snap-frozen chordoma specimens. The protease was immunohistochemically expressed by the tumor cells. The immunoreactions were accentuated at the tumor invasion fronts. Enzyme histochemistry indicated a strong tumor cell-associated cathepsin K activity in invasive tumor components. In contrast to chordoma, cathepsin K was not significantly expressed in chorda dorsalis and chondrosarcoma of the skull base. In chondrosarcoma, protease expression was limited to osteoclastic cells localized between infiltrative tumor components and regular bone trabeculae. This study shows the significant expression and activity of cathepsin K in chordoma and implicates an important and direct role of this protease in the infiltrative growth of this tumor. This protease expression occurred during neoplastic transformation and did not appear in chorda dorsalis.
Cathepsin K↗