Neuromuscular Compromise Research Articles

689: POST-EXTUBATION DYSPHAGIA IN CHILDREN AFTER MECHANICAL VENTILATORY SUPPORT

Introduction: Post-extubation dysphagia (PED) is prevalent among critically ill adult patients after mechanical ventilatory support and is associated with significant morbidity including aspiration pneumonia, alteration of feeding, malnutrition, decreased quality of life, prolonged hospitalization and mortality. Sparse studies exist detailing the prevalence, contributing risk factors and health-related outcomes of PED in critically ill children. Methods: Single-center, retrospective chart review of patients without a pre-existing dysphagia diagnosis admitted to the pediatric intensive care unit at Shands Children’s Hospital at University of Florida from June 2015 through June 2020. Patients with instrumental dysphagia evaluations after >24 hours of mechanical ventilatory support were included in the data analysis and categorized based on the presence of aspiration or dysphagia. This study aimed to determine PED prevalence, demographic and intubation risk factors contributing to PED, and the impact PED on health-related outcomes. Results: There were 36 patients included in the analysis (median age: 5 years). 72% of patients were emergently intubated (median number of attempts: 2; 86% with cuffed endotracheal tube) with a median duration of 11.5 days of mechanical ventilatory support. Aspiration was present in 64% (n=23) of the cohort. 92% (n=21) of patients with PED were silent aspirators. No demographic (age, weight, sex, pre-existing conditions) or intubation risk factors (intubation attempts, duration of mechanical ventilation, presence of cuffed endotracheal tube, endotracheal tube size) were significantly associated with the development of PED (p>0.05). Patients with PED were more likely to be re-intubated secondary to weakness or neuromuscular compromise (p=0.04). There was no significant association between PED and in-hospital mortality. However, PED was significantly associated with the need for home oxygen after discharge (p=0.03; OR 6.25; 95%CI 1.3-29.4), and modification of home feeds at both ICU (p=0.001; OR 15.0; 95% CI 2.8-81.4) and hospital discharge (p=0.001; OR 16.8; 95%CI 2.7-104.8). Conclusions: PED is prevalent and associated with worse-health related outcomes among critically ill children after mechanical ventilatory support.

HYPOTHERMIC EMERGENCY

SESSION TITLE: Medical Student/Resident Critical Care Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Hypothermia is defined as a core temperature below 95℉. The causes for hypothermia can be divided into two categories, impaired thermoregulation and increased heat loss. Increased heat loss can result from disorders that impair the skin barrier, heat stroke, cold exposure, and shock. Central failure, peripheral failure, hypothyroidism, hypoglycemia, and neuromuscular compromise are examples of causes secondary to impaired thermoregulation. In a severe state of hypothyroidism, known as myxedema coma, low thyroid hormone levels lead to a decrease in basal metabolic rate impairing thermogenesis. CASE PRESENTATION: A 65 year old male was brought to the hospital after being found unresponsive, lying outdoors for an unknown amount of time while temperatures were below freezing. Upon presentation to the ED, the patient was found to be obtunded, hypothermic to 80.6 F, bradycardic, and hypotensive. The patient's presentation was assumed to be from extended cold exposure and rewarming was initiated. He was intubated for airway protection, started on vasopressors, and admitted to the medical intensive care unit.Further work up showed an acute kidney injury, hyperkalemia, lactic acidosis, and rhabdomyolysis. His endocrine studies showed an elevated thyroid stimulating hormone (TSH) of 28.14, an undetectable triiodothyronine (T3) and thyroxine (T4), and abnormally normal cortisol. The patient was diagnosed with myxedema coma (MC) and started on an IV of liothyronine and levothyroxine as well as stress dose steroids for presumed adrenal insufficiency. Eight days after this presentation and after the initiation of thyroid hormone therapy, his mental status improved and he was successfully extubated. He was ultimately discharged to a skilled nursing facility 5 weeks later. DISCUSSION: Given several mechanisms contributing to the development of hypothermia, it is imperative to be conscious of endocrine disorders which can impair thermoregulation. MC is a medical emergency with a reported incidence of 0.22 per million per year in the Western world and a mortality rate as high as 60%. Mortality decreases to 20%–40% in treated individuals mainly as a result of clinician awareness, improvements in diagnostic testing, and advances in intensive care. If diagnostic criteria for MC is met, initiation of appropriate therapy should not be delayed as results of endocrine testing may not be readily available. CONCLUSIONS: Despite the high mortality rate associated with MC, due to prompt management in the intensive care unit with appropriate therapy of glucocorticoids and thyroxine, this patient's condition improved. We wish to emphasize the need for early detection and treatment of endocrine emergencies. In patients with severe hypothermia, initial steps for resuscitation efforts should also include early treatment of MC due to the associated mortality benefit. Reference #1: Zafren, Ken. "Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia.” Emergency Medicine Clinics of North America, vol. 35, no. 2, 2017, pp. 261–279., https://doi.org/10.1016/j.emc.2017.01.003. Reference #2: Brown, Douglas J.a. "Accidental Hypothermia.” New England Journal of Medicine, vol. 367, no. 20, 2012, pp. 1930–1938., https://doi.org/10.1056/nejmra1114208. Reference #3: Wall CR. Myxedema coma: diagnosis and treatment. Am Fam Physician. 2000;62(11):2485-2490. DISCLOSURES: No relevant relationships by Michael Blaj, source=Web Response No relevant relationships by Priyanka Durai, source=Web Response No relevant relationships by Jennifer Lindsey, source=Web Response No relevant relationships by Daisy Ngwainmbi, source=Web Response No relevant relationships by Luis Rauseo Lopez, source=Web Response

Hypophosphatemia in Refeeding Syndrome in Intrauterine Growth Restricted IUGR Neonates Who are Receiving Nutrition: A Prospective Observational Study

Objective: Electrolyte dysregulations particularly hypophosphatemia and hypokalemia following feeds in a starved person is known as refeeding syndrome, which may lead to life-threatening conditions like arrhythmias, heart failure, respiratory and neuromuscular compromise. To evaluate electrolyte dyscrasias following enteral or parenteral feeding, among intrauterine growth retardation (IUGR) neonates ie those who were starved in-utero, compared to non-IUGR neonates this study was planned.
 Methodology: From March to August 2015, 60 IUGR and non-IUGR neonates who were admitted at birth before starting of nutrition, either by breast milk or electrolyte-free intravenous fluid. An infant was classified as IUGR when his birth weight was <10th percentile according to Fenton or Lubchenco growth charts. Venous blood was collected from intramural babies at zero hours of life or just before starting feeds to determine the basal level of serum electrolytes – phosphorus, magnesium and potassium, and was repeated in the following 48 and 72 hours.
 Results: There was no significant difference between the two groups based on sex, history of maternal pre-eclampsia and oligohydramnios. At 72 hours after the start of feeding, Hypophosphatemia was significantly more prevalent, in 33.33% of IUGR vs. 2% of the non-IUGR group, [RR-5, p = 0.010]. Hypokalemia 20% IUGR; 1% non-IUGR group, [RR-6, p = 0.103]. Hypomagnesemia 3% IUGR; 2% non-IUGR group, [RR-1.5, p = 0.640]. Combined electrolyte– hypophosphatemia with hypokalemia (6.6%) and hypophosphatemia with Hypomagnesemia (13.3%), were present only in the IUGR group. Hyperglycemia was not present in any neonate. 
 Conclusions: IUGR neonates are more likely to develop Refeeding syndrome when compared to non-IUGR babies, manifesting as decreased phosphorus, potassium and magnesium levels. Phosphorous should be a part of feeding nutrition in IUGR babies.

Sarcopenia.

Sarcopenia is defined as a combination of low muscle mass with low muscle function. The term was first used to designate the loss of muscle mass and performance associated with aging. Now, recognized causes of sarcopenia also include chronic disease, a physically inactive lifestyle, loss of mobility, and malnutrition. Sarcopenia should be differentiated from cachexia, which is characterized not only by low muscle mass but also by weight loss and anorexia. Sarcopenia results from complex and interdependent pathophysiological mechanisms that include aging, physical inactivity, neuromuscular compromise, resistance to postprandial anabolism, insulin resistance, lipotoxicity, endocrine factors, oxidative stress, mitochondrial dysfunction, and inflammation. The prevalence of sarcopenia ranges from 3% to 24% depending on the diagnostic criteria used and increases with age. Among patients with rheumatoid arthritis 20% to 30% have sarcopenia, which correlates with disease severity. Sarcopenia exacts a heavy toll of functional impairment, metabolic disorders, morbidity, mortality, and healthcare costs. Thus, the consequences of sarcopenia include disability, quality of life impairments, falls, osteoporosis, dyslipidemia, an increased cardiovascular risk, metabolic syndrome, and immunosuppression. The adverse effects of sarcopenia are particularly great in patients with a high fat mass, a condition known as sarcopenic obesity. The diagnosis of sarcopenia rests on muscle mass measurements and on functional tests that evaluate either muscle strength or physical performance (walking, balance). No specific biomarkers have been identified to date. The management of sarcopenia requires a multimodal approach combining a sufficient intake of high-quality protein and fatty acids, physical exercise, and antiinflammatory medications. Selective androgen receptor modulators and anti-myostatin antibodies are being evaluated as potential stimulators of muscle anabolism.

Neuromuscular compromise in OA: more than disuse atrophy?

There is abundant evidence that the neuromuscular system is compromised in osteoarthritis (OA). Although some neuromuscular compromise occurs with aging, these deficits are even more pronounced in OA. A healthy neuromuscular system is pivotal in maintaining an optimal biomechanical environment for the musculoskeletal system. This presentation will discuss the role of neuromuscular deficits in the pathophysiology of OA, examine the potential relationships between these deficits, and propose directions for future research.

Tracheostomy in pediatric critically ill patients.

The indications for and timing of tracheostomy in children have changed significantly over recent years, and no consensus has been gathered in that regard. The purpose of this study is to present a series of critically ill patients who required a tracheostomy. All critically ill patients required a tracheostomy between 1 June 2009 and 31 March 2012. It is a retrospective, observational, descriptive study. A total of 18 patients underwent tracheostomy during the period under study. The most common indication was neuromuscular compromise. The average duration of mechanical ventilation before placement of a tracheostomy was 23.8 days (0-58 days). The complications observed were minor, and no patients died from tracheostomy-related causes. All parents were trained in airway management and cardiopulmonary resuscitation. There were no serious tracheostomy-related complications in critically ill pediatric patients. The procedure was effective in the management of patients with respiratory failure, patients with neuromuscular compromise and children with upper airway obstruction.

OC-112 Nupeg (nasal unsedated seated peg) is safer and better tolerated than rig (radiologically-inserted gastrostomy) in very high risk gastrostomy candidates

<h3>Introduction</h3> Endoscopic gastrostomy (PEG) placement in patients with severe respiratory or neuromuscular compromise carries a high risk of mortality through aspiration and radiological placement (RIG) is usually preferred in this setting. We have used ‘push-PEG’ placement in high risk patients guided by nasal endoscopy, unsedated and seated at 30–45° and here we report the outcomes of this technique compared to RIG placement in high risk patients. <h3>Method</h3> Records were analysed retrospectively for all ‘push-PEGs’ placed since 2008 and compared with records of RIG placements since 2010. Indications, completion rates and complications were compared. <h3>Results</h3> 296 push-PEGs have been placed since 2008 (mostly for head and neck malignancy). 242 were placed by standard per-oral endoscopic guidance and 54 using transnasal endoscopy using a Pentax transnasal endoscope. Of the 54, 27 (50%) were NuPEGs and the other 50% received intravenous sedation (SenPEG). 53/54 (98%) were placed successfully and without complication. One sedated patient experienced a respiratory arrest that required emergency intubation and led to the development of the NuPEG technique, since when no complications have been reported. From 2010–2014, 46 RIGs have been placed. Of these, 89% were successful and uncomplicated with one colonic perforation identified. In two patients where RIG failed due to anxiety or inability to lie flat, NuPEG was performed uneventfully. As a result, NuPEG has entirely replaced RIG in our institution where no RIGs have been placed since 2013. <h3>Conclusion</h3> NuPEG is safer and better tolerated than RIG in patients with respiratory or neuromuscular compromise and is the technique of choice in high risk patients requiring gastrostomy placement. <h3>Disclosure of interest</h3> None Declared.

Architectural and biochemical adaptations in skeletal muscle and bone following rotator cuff injury in a rat model.

Injury to the rotator cuff can cause irreversible changes to the structure and function of the associated muscles and bones. The temporal progression and pathomechanisms associated with these adaptations are unclear. The purpose of this study was to investigate the time course of structural muscle and osseous changes in a rat model of a massive rotator cuff tear. Supraspinatus and infraspinatus muscle architecture and biochemistry and humeral and scapular morphological parameters were measured three days, eight weeks, and sixteen weeks after dual tenotomy with and without chemical paralysis via botulinum toxin A (BTX). Muscle mass and physiological cross-sectional area increased over time in the age-matched control animals, decreased over time in the tenotomy+BTX group, and remained nearly the same in the tenotomy-alone group. Tenotomy+BTX led to increased extracellular collagen in the muscle. Changes in scapular bone morphology were observed in both experimental groups, consistent with reductions in load transmission across the joint. These data suggest that tenotomy alone interferes with normal age-related muscle growth. The addition of chemical paralysis yielded profound structural changes to the muscle and bone, potentially leading to impaired muscle function, increased muscle stiffness, and decreased bone strength. Structural musculoskeletal changes occur after tendon injury, and these changes are severely exacerbated with the addition of neuromuscular compromise.

Poster 250 Pain Relief for Plantar Fasciitis after Hydrodissection of Plantar Fascia from Pseudofascia: A Case Report

Disclosures: T. P. DeWald, No Disclosures: I Have No Relevant Financial Relationships to Disclose. Case Description: A right-hand-dominant 23-year-old male swimmer presented with persistent right shoulder pain, numbness, and paresthesia with radiation down the medial aspect of the right upper extremity. Patient stated that symptoms started gradually over a week and would only present during distances over 1,000 meters. Symptoms resolved when the athlete ceased activity. Setting: University Sports Medicine Clinic. Results or Clinical Course: Patient was treated conservatively with observation. Patient demonstrated normal physical examination. However, patient’s symptoms were reproduced with his right arm fully abducted and externally rotated and equivocal Adson’s test. Venous and arterial ultrasounds of the right upper extremity were obtained with no evidence of vessel obstruction. IR angiogram was then performed and did not show venous or arterial thoracic outlet syndrome. However, during provocative maneuver of extreme abduction and external rotation patient exhibited compression of the bilateral axillary arteries and circumflex humeral arteries. MRI of the right shoulder was negative for fat atrophy of teres minor and infraspinatus mucles. Electrodiagnostic studies did not demonstrate abnormalities in the axillary, ulnar, or median nerves with normal EMG of corresponding muscles. Patient resumed activity and continued to swim competitively with modification in training duration and regimen, demonstrating improvement in symptoms. The athlete will be evaluated for possible surgical decompression in the offseason. Discussion: Quadrilateral space syndrome is a rare condition arising from the compression of the axillary nerve and posterior circumflex humeral artery within the quadrilateral space. Ours is a unique case in which an athlete is demonstrating transient, ischemic quadrilateral space syndrome after long distance swimming. Muscle hypertrophy or fibrotic band formation have been implicated in pathology. Surgical decompression has proven to be successful in alleviating symptoms. Conclusions: Quadrilateral space syndrome should be considered as a differential diagnosis in young athletes with persistent shoulder pain and neuromuscular compromise as it can be missed.

Élaboration d’un score prédictif de tuberculose pulmonaire (TB) chez des patients suspects de tuberculose : une étude cas-témoin

Sarcopenia is defined as a combination of low muscle mass with low muscle function. The term was first used to designate the loss of muscle mass and performance associated with aging. Now, recognized causes of sarcopenia also include chronic disease, a physically inactive lifestyle, loss of mobility, and malnutrition. Sarcopenia should be differentiated from cachexia, which is characterized not only by low muscle mass but also by weight loss and anorexia. Sarcopenia results from complex and interdependent pathophysiological mechanisms that include aging, physical inactivity, neuromuscular compromise, resistance to postprandial anabolism, insulin resistance, lipotoxicity, endocrine factors, oxidative stress, mitochondrial dysfunction, and inflammation. The prevalence of sarcopenia ranges from 3% to 24% depending on the diagnostic criteria used and increases with age. Among patients with rheumatoid arthritis 20% to 30% have sarcopenia, which correlates with disease severity. Sarcopenia exacts a heavy toll of functional impairment, metabolic disorders, morbidity, mortality, and healthcare costs. Thus, the consequences of sarcopenia include disability, quality of life impairments, falls, osteoporosis, dyslipidemia, an increased cardiovascular risk, metabolic syndrome, and immunosuppression. The adverse effects of sarcopenia are particularly great in patients with a high fat mass, a condition known as sarcopenic obesity. The diagnosis of sarcopenia rests on muscle mass measurements and on functional tests that evaluate either muscle strength or physical performance (walking, balance). No specific biomarkers have been identified to date. The management of sarcopenia requires a multimodal approach combining a sufficient intake of high-quality protein and fatty acids, physical exercise, and antiinflammatory medications. Selective androgen receptor modulators and anti-myostatin antibodies are being evaluated as potential stimulators of muscle anabolism.

Skeletal muscle fibrosis and stiffness increase after rotator cuff tendon injury and neuromuscular compromise in a rat model.

Rotator cuff tears can cause irreversible changes (e.g., fibrosis) to the structure and function of the injured muscle(s). Fibrosis leads to increased muscle stiffness resulting in increased tension at the rotator cuff repair site. This tension influences repairability and healing potential in the clinical setting. However, the micro- and meso-scale structural and molecular sources of these whole-muscle mechanical changes are poorly understood. Here, single muscle fiber and fiber bundle passive mechanical testing was performed on rat supraspinatus and infraspinatus muscles with experimentally induced massive rotator cuff tears (Tenotomy) as well as massive tears with chemical denervation (Tenotomy + BTX) at 8 and 16 weeks post-injury. Titin molecular weight, collagen content, and myosin heavy chain profiles were measured and correlated with mechanical variables. Single fiber stiffness was not different between controls and experimental groups. However, fiber bundle stiffness was significantly increased at 8 weeks in the Tenotomy + BTX group compared to Tenotomy or control groups. Many of the changes were resolved by 16 weeks. Only fiber bundle passive mechanics was weakly correlated with collagen content. These data suggest that tendon injury with concomitant neuromuscular compromise results in extra-cellular matrix production and increases in stiffness of the muscle, potentially complicating subsequent attempts for surgical repair.

Guided Growth for Fixed Knee Flexion Deformity

Fixed knee flexion deformity (FKFD) is an insidious problem that may complicate the management of patients with neuromuscular compromise due to cerebral palsy, spina bifida, arthrogryposis, and other conditions. The energy costs associated with crouch gait may become prohibitive and, with the inexorable progression of fixed knee flexion, secondary pain may ensue as a result of fragmentation of the patella and/or tibial tubercle. Concomitant or compensatory flexion deformity of the hips and lumbar lordosis may develop, along with "pseudo equinus" of the ankles. Recommended treatments for FKFD have included bracing; physical therapy; and, in recalcitrant cases, distal femoral osteotomy, posterior release, or frame distraction. However, these latter modalities are fraught with potential complications including neurovascular damage, loss of fixation, undercorrection malunion, fracture, and recurrent deformity. Considering that FKFD is often bilateral, the complication risks for a given patient are doubled. In a previous study, the senior author reported successful hemiepiphysiodesis of the distal anterior femur using staples. However, further experience has demonstrated some of the limitations of stapling including relatively slow correction and occasional hardware migration. This led to the development of a more versatile and reliable solution using a pair of anterior tension band plates. In this retrospective clinical study, we are reporting this new technique of promoting gradual correction through guided growth of the distal femur, using a pair of anterior 8-plates. The correction is accomplished simultaneously and bilaterally, without immobilization, and may be combined with other operative procedures as indicated. We reviewed the charts, radiographs in a group of patients treated accordingly. In this group of 18 patients with 29 deformities, we noted correction averaging 1.3 degrees (range, 0.0 [1 patient]-4.8 degrees), with minimal complications. No inadvertent coronal plane deformities were created. Upon full correction, the plates were removed so as to avoid recurvatum. As an alternative to posterior capsulotomy or supracondylar extension osteotomy, we have found that guided growth is an effective and safe method of gradually correcting FKFD in growing children and adolescents. 4 (retrospective clinical series).

Relaxing hip precautions increased patient satisfaction and promoted quicker return to normal activities after total hip arthroplasty

Peak EL, Parvizi J, Ciminiello M, et al . The role of patient restrictions in reducing the prevalence of early dislocation following total hip arthroplasty. A randomized, prospective study. J...

BLADDER GROWTH AND DEVELOPMENT AFTER COMPLETE PRIMARY REPAIR OF BLADDER EXSTROPHY IN THE NEWBORN WITH COMPARISON TO STAGED APPROACH

We assessed bladder growth and dynamics following complete primary repair of bladder exstrophy (CPRE) compared to the staged approach. We reviewed the records of 16 boys and 7 girls who underwent CPRE within 3 days of life from 1996 to 2004 and compared them to the records of 8 boys and 6 girls treated with a staged repair from 1979 to 1996. Screening methods included voiding cystourethrogram, radionuclide cystogram and urodynamic study. We estimated growth curves for bladder capacity following repair in each group, and compared percent predicted bladder capacity (PPBC), compliance and detrusor overactivity between the CPRE and staged repair groups following bladder neck reconstruction. Bladder capacity in the staged repair group was 69.8 ml (95% CI 46.7-104.4) immediately after bladder neck reconstruction and increased by 15.0% per year thereafter (95% CI 6.2-24.5, p = 0.002). In the CPRE group bladder capacity was 29.0 ml (95% CI 21.3-39.5) initially and increased by 28.9% per year thereafter (95% CI 17.4-41.5, p <0.001). PPBC started at 45.6% (95% CI 35.7-55.5) and increased 1.2% per year (95% CI -1.1-3.5, p = 0.29) following repair for all genders and surgery groups. Compliance was 124.4% (95% CI 22.6-310.7, p = 0.01) greater in the CPRE group at all times following repair. Detrusor overactivity was present in 0 of 19 patients in the CPRE group and 6 of 13 (46%) in the staged group (exact p = 0.002). Within the CPRE group bladder stability was universal, and sphincter electromyography was normal suggesting no neuromuscular compromise of the pelvic floor. At early followup, our results suggest that PPBC is equivalent irrespective of gender or management. Further objective evaluation is needed in both groups.

A limited anterior petrosectomy with preoperative embolization of the inferior petrosal sinus for ventral brainstem tumor removal

BACKGROUND The present study describes the use of a limited subtemporal extradural anterior petrosectomy with preoperative embolization of the inferior petrosal sinus for the management of tumors located behind the clivus and ventral to the brainstem. Details of the procedure and its application in five cases are presented. METHODS This procedure consists of using the extradural route to approach the upper side of the petrosal pyramid so that it can be drilled medially, and to resect the apex to come out into the posterior fossa. This route gives a petrosectomy just medial to the horizontal segment of the petrous carotid artery in front of the cochlea. It goes around the labyrinthine mass and the internal auditory canal from above to expose the posterior fossa dura between the two petrosal sinuses. The dural opening exposes the ventral aspect of the pons from the trigeminal nerve to the origin of the abducens nerve, ventral to the facial nerve. Preoperative embolization of the inferior petrosal sinus allows its intraoperative section for a wider exposure along the lower clivus. This approach can easily be combined with an intradural approach to provide additional exposure above the trigeminal nerve. Patients who underwent this procedure had prepontine cisternal chordoma or epidermoid cyst of the petroclival region. RESULTS One patient experienced a cranial nerve deficit as a direct result of the surgical procedure (VIth nerve palsy requiring surgery) but no other patient has had permanent neuromuscular compromise. Complications consisted of a wound infection in one case. Tumor removal was total in three cases and partial in two cases. CONCLUSION Quite easy to master, the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and preserving hearing.

P-3-335 - New development of a cranionavigation system for skull base surgery (“cranionavigator”)

BACKGROUNDThe present study describes the use of a limited subtemporal extradural anterior petrosectomy with preoperative embolization of the inferior petrosal sinus for the management of tumors located behind the clivus and ventral to the brainstem. Details of the procedure and its application in five cases are presented.METHODSThis procedure consists of using the extradural route to approach the upper side of the petrosal pyramid so that it can be drilled medially, and to resect the apex to come out into the posterior fossa. This route gives a petrosectomy just medial to the horizontal segment of the petrous carotid artery in front of the cochlea. It goes around the labyrinthine mass and the internal auditory canal from above to expose the posterior fossa dura between the two petrosal sinuses. The dural opening exposes the ventral aspect of the pons from the trigeminal nerve to the origin of the abducens nerve, ventral to the facial nerve. Preoperative embolization of the inferior petrosal sinus allows its intraoperative section for a wider exposure along the lower clivus. This approach can easily be combined with an intradural approach to provide additional exposure above the trigeminal nerve. Patients who underwent this procedure had prepontine cisternal chordoma or epidermoid cyst of the petroclival region.RESULTSOne patient experienced a cranial nerve deficit as a direct result of the surgical procedure (VIth nerve palsy requiring surgery) but no other patient has had permanent neuromuscular compromise. Complications consisted of a wound infection in one case. Tumor removal was total in three cases and partial in two cases.CONCLUSIONQuite easy to master, the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and preserving hearing.

Effects of chronic carbon disulfide inhalation on sensory and motor function in the rat

Chronic carbon disulfide (CS 2) exposure produces debilitating motor, sensory and neuropsychiatric consequences in humans. Sensory, especially auditory, tests have been considered for indexing early intoxication. This study examines effects of chronic CS 2 exposure in rat upon auditory and neuromuscular function using reflex modulation audiometry to test the feasibility of using pure tone detection thresholds as such an index. This method is sensitive to the differential effects of toxicants upon acoustic and neuromuscular functioning. Rats were tested before, during and after five or 12 weeks of 500 ppm CS 2 inhalation, six h/day, five days/week. Neuromuscular integrity, reflected by baseline startle amplitude, decreased 50% after five weeks and 67% following 12 weeks of CS 2 exposure; recovery to 70% of preexposure values occurred on the fourth postexposure week. Twelve weeks of CS 2 inhalation had no significant effect upon acoustic thresholds. Pure tone detection thresholds, therefore, do not appear adequate to index early CS 2 exposure levels in the rat, as severe neuromuscular compromise occurred at a time when acoustic thresholds remained stable.

Serum Creatine Kinase in the Post-Polio Population

Elevated creatine kinase (CK) levels may be noted in neuromuscular patients as a result of muscle damage and necrosis. We measured the serum CK levels of 62 post-polio patients with chronic neurologic disease (Neuro) and 13 post-polio patients with no evidence of neurologic compromise (Control). Patient groups were comparable for age, gender and years since onset of poliomyelitis. The Neuro group had substantially increased CK levels compared with the Control group, 211 +/- 19.0 IU v 114 +/- 26.2 IU (mean +/- 1 SE; P less than 0.05). Of the Neuro group, 40% had abnormally elevated CK values, compared with 8% of the Control group. Within the Neuro group, there was a robust correlation between elevated CK values and self-reports of strenuous work and level of community ambulation (P less than 0.05). These findings support the hypothesis that chronic muscle overuse may be a contributing factor to the advanced senescence reported by post-polio patients with neuromuscular compromise.

358 EFFECT OF GENTAMICIN ON NEUROMUSCULAR FUNCTION (NMF) OF A HYPERMAGNESEMIC NEONATE

Treatment of maternal pre-eclampsia with MgSO4 is reported to produce flaccidity, lethargy and hyporeflexia in their infants. Aminoglycosides can also affect NMF. Both agents interfere with release of acetylcholine, producing a defect in neuromuscular transmission. A term infant was born to a pre-eclamptic mother treated with 28 gm MgSO4. The baby had cord blood Mg++ of 3.9 mg/d1 and demonstrated neuromuscular compromise as measured by ulnar nerve stimulation studies and neurologic examination. Improvement occurred as serum Mg++ level approached normal (1.5 ± 0.2 mg/d1). At 48 hrs. of age, septicemia was suspected and antibiotics (ampicillin 50 mg/kg IV q 12 hrs. and gentamicin 2.5 mg/kg IV q 12 hrs.) begun. Two hours after receiving the second dose of gentamicin, the infant had respiratory, followed by cardiac arrest. Resuscitation was successful and 24 hrs. later NMF was studied before and after a gentamicin dose. Increasing fatigability of NMF occurred at 1 and 2 hrs. after gentamicin. This case suggests that depressed NMF in a hypermagnesemic infant may be further compromised by aminoglycoside therapy.