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Brain stem epidermoid cysts are extremely rare lesions. Only nine cases have been reported. Management of the epidermoid cyst is decompression of cyst contents and removal of cyst capsule. But in some cases resection of the cyst may result in a poor outcome because of cyst wall adhesion into the brain stem.
Brain-stem auditory evoked potentials were measured in 14 comatose patients treated with aminoglycosides in cases of bronchopulmonary infection. Patients treated with tobramycin showed little influences on the latencies of wave 1, whereas treatment with amikacin resulted in enhanced wave 1 latencies even after completion of therapy. These changes were observed with therapeutic plasma levels of the aminoglycosides in all cases. As a method of bedside monitoring of auditory function with no additional stress to the patient with immediate results monitoring brain-stem auditory evoked potentials is recommended as a routine method to control auditory function in comatose patients under administration of aminoglycosides.
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Auditory brainstem potentials were recorded in 22 comatose patients in whom the level of brainstem dysfunction was defined by the clinical assessment of brainstem reflexes and posture. The patients with cortico-subcortical or diencephalic levels showed normal brainstem potentials. The other patients showed a relationship between the abnormalities of the different components of the brainstem potentials and the clinical levels of brainstem dysfunction caused by the rostro-caudal evolution. Alteration of wave V seemed to be related to a midbrain dysfunction, alteration of wave III to a pontine dysfunction and alteration of waves I and II to a lower brainstem dysfunction.
Despite improved brain-stem imaging by magnetic resonance and high-resolution x-ray computerized tomography, definitive diagnosis and therapy of intrinsic lesions of the brain stem require histological verification. A stereotaxic approach to brain-stem lesions provides a high yield of positive histological diagnosis with a low incidence of morbidity. A series of 14 stereotaxic procedures performed on 12 patients with intrinsic lesions of the mesencephalon, pons, and medulla is reviewed. A detailed description of the transfrontal approach used by the authors is presented. Definitive pathological diagnosis was obtained in all patients. There was no operative mortality and only one case of permanent neurological deficit. The significance of accurate histological diagnosis in the therapy of brain-stem lesions is discussed.
BACKGROUND: Brain stem dermoid cysts are very rare lesions, and in most, the outcome has been very poor. Because of the dangers of dissecting the cyst wall away from the brain stem parenchyma, some authors have advocated not to attempt a radical resection. METHODS: We describe a child in whom the brain stem dermoid cyst recurred rapidly after a conservative approach. We therefore attempted a radical removal. RESULTS: During surgery, the almost complete resection of the cyst wall was not very difficult, leading to an apparent cure after 4 years. CONCLUSION: In exceptional cases, it may be possible to remove a brain stem dermoid cyst without prohibitive morbidity and with long-term cure.
Dorsally exophytic brain-stem gliomas represent a distinctive subgroup of pediatric brain-stem neoplasms that are amenable to radical excision because of their benign histology and growth characteristics. However, their attachment to the floor of the fourth ventricle invariably precludes complete tumor excision. The long-term behavior of the residual tumor remains a subject of concern. To address this issue, the authors reviewed their experience with 18 dorsally exophytic brain-stem gliomas treated between 1974 and 1990. At operation, the tumors filled the fourth ventricle, fungating out of a broad-based area of the dorsal brain stem. The exophytic tumor was resected, but no attempt was made to remove tumor from the brain stem. Histological examination showed that 16 of the tumors were grade I or II astrocytomas, one was a ganglioglioma, and one was an otherwise benign-appearing glioma with several foci of anaplasia that was classified as a grade III astrocytoma. The latter patient was one of only two in the series to receive postoperative radiation therapy; both cases so treated have no evidence of disease on follow-up imaging studies 61 and 135 months postoperatively. One other child who had stable disease postoperatively died of shunt malfunction 18 months after tumor excision. Serial radiographic studies in the other 15 patients have shown no evidence of disease in three, stable residual disease in eight, and tumor enlargement 12, 28, 40, and 84 months postoperatively in four (median follow-up period 113 months). Each of the four patients with tumor regrowth underwent repeat tumor excision. Two of these children received perioperative radiation therapy at the time of disease progression and both showed reduction in tumor volume 28 and 65 months after their second operation. In contrast, both patients who did not receive radiotherapy at the time of disease progression had further tumor enlargement 48 and 84 months after their second operation and underwent a third tumor resection; one received postoperative radiation therapy and has no evidence of disease 58 months after his third operation and the other child has stable disease 27 months postoperatively. Histological examination of tumor specimens obtained at second and third operations showed no change from the appearance of the tumor on the initial resection. The authors conclude that the majority of dorsally exophytic brain-stem gliomas can be managed successfully with subtotal excision and, if necessary, cerebrospinal fluid diversion. The small percentage of tumors in this series that showed recurrent growth remained benign histologically.(ABSTRACT TRUNCATED AT 400 WORDS)
Infectious lesions of the brain stem are rare and include primarily abscess and encephalitis. The most common etiologic agents for abscess formation are Streptococcus sp., Staphylococcus sp., and M. tuberculosis. Encephalitis is associated most often with L. monocytogenes and herpes simplex virus infection. Classical brain stem syndromes are uncommon with brain stem infections, and CSF obstruction can be seen with neurocysticercosis. The diagnosis of these lesions has been greatly aided by CT and MR imaging. Microsurgery and stereotaxis are both appropriate techniques for the treatment of brain stem abscess that establish a diagnosis, identify the causative agent, and relieve mass effect on important neural structures. Symptoms of hydrocephalus should be treated with temporary or permanent CSF diversion. Viral involvement of the brain stem is usually self-limited, and improved antimicrobial therapy has contributed to a decrease in the morbidity and mortality of bacterial and parasitic infections. Although once believed to be uniformly fatal, infections of the brain stem have now been successfully treated for more than a decade.
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The auditory brain-stem response (ABR) recorded from the vertex of the rat was analyzed before and after the brain was functionally isolated from the body trunk and maintained via cross-circulation. The ABR profile did not change for as long as 30 min after isolating the brain. The finding indicates that this experimental procedure is useful for studying the brain devoid of input from the trunk.
Auditory brain-stem response (ABR) results are reported on three cases of acoustic tumors and two cases with brain-stem lesions. These cases highlight several considerations in the clinical use of ABR. The sensitivity of ABR to retrocochlear involvement in light of normal pure-tone hearing and cochlear hearing loss is shown in the first two cases. The third case shows the advantage of "contralateral" ABR testing and a unique effect of stimulus polarity. The use of an intensity function and high presentation rate procedures are shown to be helpful diagnostic procedures in case four. Case five shows bilateral ABR effects which correlate well with the degree of brain-stem involvement. In addition to the ABR data, audiologic, radiologic, and medical findings on these patients are also discussed.
Brain stem evoked response (BER) audiometry presents abnormal findings in patients with acoustic neuromas. The test involves averaging of recordings at the vertex as sound-triggered nerve impulses travel from the cochlea to the brain stem. From the time the sound stimulus arrives at the cochlea until it reaches the first major brain stem synapse (within 10 milliseconds), five major waves have been identified as typical of normal averaged responses. Abnormality in the cochlea or eighth nerve causes specific changes in pattern, primarily in wave latency. These latency shifts can be used to predict the site of the lesion. In evaluating 17 lesions of the cerebellopontine angle, BER audiometry was accurate in the diagnosis of all of the tumors. This diagnostic tool should play a prominent role when acoustic tumor is suspected.
Auditory brain stem responses evoked with click stimuli of varying repetition rates (11, 31, 51, and 91 clicks/sec) and intensities but judged as being equally loud as three reference loudness levels (90, 80, and 70 phons) were examined in normal-hearing listeners. Analysis of wave component latencies and amplitudes indicated that loudness level changes are reflected in the brain stem response. However, the combined influence of stimulus rate and intensity was greater than that of perceived loudness level. It was concluded that the auditory brain stem response does not provide a direct link to loudness perception.
BAEP records were obtained from 30 brain-dead patients. Three BAEP patterns were observed: (1) no identifiable waves (73.34%), (2) an isolated bilateral wave I (16.66%), and (3) an isolated unilateral wave I (10%). When wave I was present, it was always significantly delayed. Significant augmentation of wave I amplitude was present bilaterally in one case and unilaterally in another. On the other hand, in serial records from 3 cases wave I latency tended to increase progressively until this component disappeared. During the same period, wave I amplitude fluctuations were observed. A significant negative correlation was found for wave I latency with heart rate and body temperature in 1 case. Two facts might explain the progressive delay and disappearance of wave I in brain-dead patients: a progressive hypoxic-ischaemic dysfunction of the cochlea and the eighth nerve plus hypothermia, often present in brain-dead patients. Then the incidence of wave I preservation reported by different authors in single BAEP records from brain-dead patients might depend on the moment at which the evoked potential study was done in relation to the onset of the clinical state. It is suggested that, although BAEPs provide an objective electrophysiological assessment of brain-stem function, essential for BD diagnosis, this technique could be of no value for this purpose when used in isolation.
Brain-stem auditory evoked potentials (BAEPs) are realized after the first flat EEG in 50 patients. BAEPs were absent in 70% of the patients. In 22% of the patients, one- or two-sided peak I persists. In 8% the peaks I, II and IV exist after the first flat EEG. BAEP evolution with the course of time is realized. A complete disappearance is established after 24 h. The useful advantage of BAEPs in the early diagnosis of brain death is discussed.
In patients with acoustic neuronoma or space-occupying lesion in the region of the brainstem we recorded preoperatively the brainstem potentials as well as the late potential N1. With one exception all patients investigated showed changes in the brainstem potential pattern. When stimulating monaurally there exists a clear side difference, that means the changes in the potential pattern are more distinct on the side of the tumour than on the opposite side and then only if an obstructive hydrocephalus exists. Moreover we could demonstrate in patients with tumours in the region of the brainstem that the brainstem potential IV is no longer suitable for measuring the hearing threshold. On the other hand in these patients an exact determination of the hearing threshold is possible with the late potential N1. Altogether the findings show, that the recording of the brainstem potentials when stimulating monaurally is an important additional diagnostic tool to recognize impairment of the acoustic pathways within the brainstem and probably affords the possibility of perceiving pathological pressure within the brain.
OBJECT: Most patients diagnosed with brain stem glioma become bedridden because of deteriorating brain stem function. Many brain stem glioma patients develop hydrocephalus. Both of these outcomes greatly detract from the quality of life of these patients. We have analyzed the occurrence of hydrocephalus in diffuse brain stem gliomas in children, and we discuss the management of advanced cases. METHODS: Eighteen patients diagnosed with brain stem glioma while under 15 years of age, including 1 with dissemination, were studied retrospectively. The average overall survival was 11.8 +/- 6.5 months (mean +/- SD). Hydrocephalus occurred in 16 (88.9%) of the 18 cases. The patients diagnosed with hydrocephalus all exhibited a rapid decline in consciousness. The average time to onset of hydrocephalus after tumor diagnosis was 5.1 +/- 3.3 months. Twelve of the 16 patients with hydrocephalus were treated with cerebrospinal fluid (CSF) diversion, by means of a Torkildsen shunt, a ventriculoperitoneal shunt, or third ventriculostomy. The level of consciousness and patient performance status improved after CSF diversion except in 2 patients who had received Torkildsen shunts. The patients treated for hydrocephalus survived significantly longer than those patients who did not undergo any intervention for hydrocephalus. CSF diversion may be a therapeutic intervention that significantly improves the quality of life and survival of patients. CONCLUSION: Our results suggest that patients diagnosed with brain stem glioma should be closely monitored for signs of hydrocephalus and be examined by neuroimaging rapidly when indicated. Our results also suggest that once hydrocephalus is diagnosed CSF diversion should be performed promptly.
Successful surgery within the brain stem parenchyma demands precise knowledge of the surface anatomy, relationship between surface and deep structures, microscopic anatomy, and functional anatomy of the brain stem. Emphasis on correlative knowledge of these aspects of brain stem anatomy will improve the success of brain stem surgery.