Biomedical subjects

J F Hahn

Publications and source records attributed to J F Hahn.

At least 37 records · Page 2Linked to original sources

PubMed1987

Acoustic (loudspeaker) facial EMG monitoring: II. Use of evoked EMG activity during acoustic neuroma resection.

Facial electromyographic (EMG) activity was continuously monitored via loudspeaker during eleven translabyrinthine and nine suboccipital consecutive unselected acoustic neuroma resections. Ipsilateral facial EMG activity was synchronously recorded on the audio channels of operative videotapes, which were retrospectively reviewed in order to allow detailed evaluation of the potential benefit of various acoustic EMG patterns in the performance of specific aspects of acoustic neuroma resection. The use of evoked facial EMG activity was classified and described. Direct local mechanical (surgical) stimulation and direct electrical stimulation were of benefit in the localization and/or delineation of the facial nerve contour. Burst and train acoustic patterns of EMG activity appeared to indicate surgical trauma to the facial nerve that would not have been appreciated otherwise. Early results of postoperative facial function of monitored patients are presented, and the possible value of burst and train acoustic EMG activity patterns in the intraoperative assessment of facial nerve function is discussed. Acoustic facial EMG monitoring appears to provide a potentially powerful surgical tool for delineation of the facial nerve contour, the ongoing use of which may lead to continued improvement in facial nerve function preservation through modification of dissection strategy.

Adult↗

PubMed1987

Normal pressure hydrocephalus in children and young adults.

Normal pressure hydrocephalus (NPH) is generally considered to be a disorder of adult and geriatric patients. We report four patients who are children or young adults with chronic neurological disorders, recent deterioration of their levels of function, normal cerebrospinal fluid (CSF) pressures, and ventricular enlargement. All four patients improved after the placement or revision of a ventriculoperitoneal shunt. Frequent symptoms and signs included irritability (three patients), vomiting (three patients), and abnormal limb posturing (two patients). Correct diagnosis was hampered by two factors: (a) Multiple or prolonged recordings of CSF pressures were invariably well within the normal ranges with respect to age, and (b) the patients had chronic neurological deficits. After ventriculoperitoneal shunting, subjective and objective improvement was seen in all cases. Young patients with large ventricles may benefit from shunting procedures despite low CSF pressures. These patients may be clinically identified by symptoms of new neurological dysfunction in cases of previously static neurological disease or acceleration of slowly progressive neurological dysfunction. Some of these underlying neurological disorders may predispose children and young adults to NPH.

Adult↗

PubMed1986

Magnetic resonance imaging (1.5 tesla) in patients with intractable focal seizures.

Magnetic resonance (MR) (1.5 tesla) studies were performed in ten patients with temporal lobe epilepsy and two with temporofrontal epilepsy. Two patients with temporal lobe epilepsy and one with temporofrontal epilepsy exhibited areas of increased signal intensity on T2-weighted images in the mesiobasal portion of the temporal lobe shown by electroencephalography to be the epileptogenic focus; no analogous abnormalities had been found in these patients on computed tomographic scans. Pathologic studies have not revealed a specific ultrastructural correlate for the MR findings in this group of patients. We found MR to be a useful, noninvasive diagnostic adjunct in the presurgical assessment of some patients with temporal lobe epilepsy. Where abnormalities were found, they corresponded with the epileptogenic focus as defined by electroencephalography.

Adult↗

PubMed1986

Postoperative neurological deficits may occur despite unchanged intraoperative somatosensory evoked potentials.

We describe 6 patients who demonstrated postoperative neurological deficits despite unchanged somatosensory evoked potentials during intraoperative monitoring. Although there is both experimental and clinical evidence that somatosensory evoked potentials are sensitive to some types of intraoperative mishap, the technique should be employed with an awareness of its possible limitations.

Adolescent↗

PubMed1986

Neurophysiological techniques as an aid to surgical treatment of primary brain tumors.

We describe a method of cortical stimulation for localizing functional areas of brain before operation for primary brain tumors that was carried out in 14 patients. The method is unique in that the stimulation is done over several days using chronically indwelling subdural electrode arrays. In addition to cortical stimulation findings, somatosensory evoked potentials were helpful in locating the sensorimotor strip. The neurophysiological data have allowed an aggressive neurosurgical attack without producing a functional deficit.

Adolescent↗

PubMed1986

Symptomatic subependymoma in a 14-year-old girl, diagnosed by NMR scan.

Symptomatic subependymomas in the pediatric age group are rare. A 14-year-old girl with a IV ventricle subependymoma is described. She had a 2-month history of progressive headache, neck stiffness and nausea. Computed tomography revealed hydrocephalus for which a ventriculoperitoneal shunt was inserted. A nuclear magnetic resonance (NMR) scan later displayed a mass lesion in the roof of the IV ventricle. A suboccipital craniectomy was performed with total excision of a subependymoma.

Adolescent↗

PubMed1986

Pituitary apoplexy: a complication of cardiac surgery.

Pituitary apoplexy occurred in 3 patients in the immediate postoperative period following cardiac operation with cardiopulmonary bypass. In this setting, this complication is extremely rare and not widely recognized. Precipitating factors may be related to the extracorporeal bypass apparatus, anticoagulation, low cerebral blood flow, and even anesthetic agents. Neurosurgical decompression can be safely performed in the early postoperative period following open-heart operations.

Cardiopulmonary Bypass↗

PubMed1986

Benign osteoblastoma of the orbit.

Benign osteoblastoma is a rare, solitary, vascular, osteoid-producing tumor that is rich in osteoblasts. This is the first report of a case of osteoblastoma of the orbit not contiguous with a sinus cavity.

Child, Preschool↗

PubMed1986

Four dichotic speech tests before and after temporal lobectomy.

Thirty patients were tested with four dichotic speech tests before and after temporal lobectomy for control of intractable seizures. Ipsilateral ear scores improved on all tests postoperatively; these improved scores reached statistical significance for the Staggered Spondaic Word Test and for consonant-vowel syllables. This result, combined with a nonsignificant decrease for contralateral ear scores, produced postoperative increase in the ipsilateral minus contralateral ear difference scores, similar to previous literature. Preoperative tests for a larger group of patients showed significantly poorer performance than for normal subjects, for all four tests. Total correct scores, used as a measure of overall auditory processing capacity, were impaired for these patients, but unchanged or slightly improved after surgery.

Adolescent↗

PubMed1986

Spinal neurofibromas: a report of 66 cases and a comparison with meningiomas.

A series of 66 spinal cord neurofibromas was analyzed for history, signs, surgical approach, and outcome. The tumors presented primarily with sensory symptoms. Plain films were abnormal in 1/2 of cases and 1/2 had a complete block. They were primarily intradural, and primarily thoracic. A conservative exam system was used for follow-up and 85% with pain had complete relief; 50% with motor loss had normal motor function, and 88% had normal sensation who had prior sensory loss. In comparison to meningiomas, the principal differences were that neurofibromas had an even sex distribution, a lower incidence of cord signs and symptoms, more frequent findings on plain x-rays, and higher cerebrospinal fluid protein. Surgical outcome was similar. Sacrifice of the involved root during removal usually did not produce a deficit. The series is compared with a similar series of meningiomas from the same institution over the same time period.

Adolescent↗

PubMed1986

Fusiform basilar artery aneurysm in a 33-month-old child.

A 33-month-old girl presented with acute subarachnoid hemorrhage from a ruptured multilobulated fusiform aneurysm of the midbasilar artery. This rare lesion was treated surgically by occluding the basilar artery. Intraoperative brain stem auditory evoked potential and somatosensory evoked potential monitoring results did not change with basilar artery occlusion, suggesting that the occlusion would be tolerated. However, the amplitudes of brain stem auditory evoked potential Waves III-V to right ear stimulation were transiently reduced during left pontine retraction during the aneurysm exposure. The patient made a complete clinical recovery.

Aneurysm↗

PubMed1986

Effect of etomidate on the electroencephalogram of patients with epilepsy.

Etomidate was given intravenously to 12 epileptic patients undergoing craniotomy for surgical removal of their seizure focus. Electroencephalograms were recorded by means of subdural electrodes. Nine of the 12 patients showed an increase in epileptiform activity. In six of the nine patients, the activity was marked.

Adolescent↗

PubMed1985

Medulloblastoma. Period of risk reviewed.

Collins postulated that patients with Wilms' tumor surviving for a period equal to their age at diagnosis plus 9 months were no longer at risk for a recurrence. Although this no longer holds for Wilms' tumor, it has been applied to patients with medulloblastoma. Case histories of patients who survived a period of risk designated by Collins' rule and later developed a histologically confirmed recurrent medulloblastoma are discussed. Reported cases violating Collins' rule constitute less than 2% of all medulloblastomas. The continued use of Collins' rule is advocated. Patients who have survived this period of risk, are neurologically stable, and have a negative computerized tomography (CT) head scan are exceedingly unlikely to develop a recurrent medulloblastoma.

Age Factors↗

PubMed1985

Muteness of cerebellar origin.

Acute bilateral damage to large areas of both cerebellar hemispheres including the dentate nuclei led to temporary loss of speech in six children. In each case muteness was unassociated with motor paralysis, loss of higher cognitive functions, or cranial nerve dysfunction. Muteness lasted one to three months. All patients were severely dysarthric during recovery. We conclude that transient muteness may result from acute bilateral cerebellar injury.

Cerebellar Diseases↗

PubMed1985

The second sensory area in humans: evoked potential and electrical stimulation studies.

A patient with intractable seizures originating from a right frontal focus was evaluated for surgical treatment. This evaluation was carried out using a chronically implanted array of 96 stainless steel electrodes 1 cm apart and covering the perirolandic and frontal areas. Somatosensory evoked potentials and electrical stimulation of the subdural electrodes localized the primary sensory hand area. Evoked potentials of identical waveform but of lower amplitude and 2.4 ms longer latency were recorded in the inferior frontal gyrus immediately anterior to the face area of the motor strip. Electrical stimulation of that area elicited: (1) a "paralyzing" feeling in the left arm and face; (2) inhibition of rapid alternating movements of left fingers, left hand, and tongue; (3) inability to maintain a strong voluntary muscle contraction of the left hand or tongue; and (4) speech arrest. This appears to be the first report of a secondary sensory area in humans demonstrated by both electrical stimulation and evoked potential studies. Electrical stimulation showed that the secondary sensory area overlapped an area of complex motor control, suggesting that the secondary sensory area provides direct sensory feedback information for appropriate motor integration.

Adult↗

PubMed1985

Enhanced DNA synthesis of human glial cells exposed to human leukocyte products.

DNA synthesis was studied in primary glial cell cultures derived from adult human non-neoplastic and neoplastic brain tissues. Enhanced DNA synthesis occurred in 5/5 non-neoplastic astrocyte, one oligodendroglioma, and 2/5 astrocytoma cultures after exposure to medium containing 1.25-12.5% supernatant fluid (SF) from insoluble concanavalin A (Con A) stimulated unseparated or T lymphocyte-enriched human mononuclear leukocytes (MNL). Analyses of SF indicated that the presence of platelet-derived growth factor (PDGF) could not account for glial cell stimulation, and exposure to semi-purified interleukin-2 (IL-2) in amounts comparable to those in SF from Con A-stimulated MNL had no effect on glial cells. These data indicate that non-neoplastic astrocytes and other human glial cells are stimulated by products of human MNL.

Astrocytoma↗

PubMed1985

Magnetic resonance of brain tumors: considerations of imaging contrast on the basis of relaxation measurements.

Proton spin-lattice and spin-spin relaxation times have been measured in surgically-removed normal CNS tissues and a variety of tumors of the brain. All measurements were made at 20 MHz and 37 degrees C. Between grey and white matter from autopsy human or canine specimens significant differences in T1 or T2 were observed, with greater differences seen in T1. Such discrimination was reduced in samples obtained from live brain-tumor patients due to lengthening in T1 and T2 of white matter near tumorous lesions. Edematous white matter showed T1 and T2 values higher than those of autopsy disease-free white matter. Compared to normal CNS tissues, most brain tumors examined in this study demonstrated elevated T1 and T2 values. Exceptions, however, did exist. No definitive correlation was indicated on a T1 or T2 basis which allowed a distinction to be made between benign and malignant states. Furthermore, considerable variation in relaxation times occurred from tumor to tumor of the same type, suggesting that within a tumor type there are important differences in physiology, biology, and/or pathologic state. Such variation caused partial overlap in relaxation times among certain tumor types and hence may limit the capability of magnetic resonance imaging (MR) alone for the diagnosis of specific disease. Nonetheless, this study predicts that on the basis of T1 or T2 differences most brain tumors are readily detectable by MR via saturation recovery or inversion recovery with appropriate selections of pulse-spacing parameters. In general, tumors can be discriminated against white matter better than grey matter and contrast between glioma and grey matter is usually superior to that between meningioma and grey matter. This work did not consider tissue-associated proton density which should be addressed together with T1 and T2 for a complete treatment of MR contrast.

Adenoma↗

PubMed1985

Potentiation of the combination of pancuronium and metocurine by halothane and isoflurane in humans with and without renal failure.

Dose-response relationships for a 1:4 weight ratio-mixture of pancuronium and metocurine were studied during inhalational anesthesia with halothane and isoflurane in patients with and without renal failure. The time for recovery from 10 to 20% of control thumb twitch tension also was determined. In subjects with normal renal function, relaxant doses required for 95% twitch height suppression (ED95) were 50% of those predicted by simple addition of effects when used with a balanced anesthetic technique, 37% of predicted when used with 1.3 MAC halothane, and 25% of predicted when used with 1.3 MAC isoflurane (P less than 0.05). In subjects with renal failure, ED95 values for the combination were 40% of predicted when used with 1.2 MAC halothane and 45% of predicted when used with 1.2 MAC isoflurane (NS). For relaxants used singly in renal failure, pancuronium alone was slightly enhanced by 1.2 MAC halothane (85% of predicted), while 1.1 MAC isoflurane reduced the ED95 to 57% of predicted (P less than 0.05). Similar results were obtained for metocurine alone when used in renal failure (77 and 58% of predicted when used with halothane and isoflurane, respectively) (NS). Predicted values are published results for balanced anesthesia in normals. Recovery times were prolonged twofold in renal failure (P less than 0.05). Thus, the combination of pancuronium and metocurine is synergistic to the same degree in normals and in renal failure patients, but the total blockade produced by the combination is enhanced by halothane and isoflurane only in normals.

Adult↗