Chest CT Image based Lung Disease Classification - A Review.

Computed tomography (CT) scans are widely used to diagnose lung conditions due to their ability to provide a detailed overview of the body's respiratory system. Despite its popularity, visual examination of CT scan images can lead to misinterpretations that impede a timely diagnosis. Utilizing technology to evaluate images for disease detection is also a challenge. As a result, there is a significant demand for more advanced systems that can accurately classify lung diseases from CT scan images. In this work, we provide an extensive analysis of different approaches and their performances that can help young researchers to build more advanced systems. First, we briefly introduce diagnosis and treatment procedures for various lung diseases. Then, a brief description of existing methods used for the classification of lung diseases is presented. Later, an overview of the general procedures for lung disease classification using machine learning (ML) is provided. Furthermore, an overview of recent progress in ML-based classification of lung diseases is provided. Finally, existing challenges in ML techniques are presented. It is concluded that deep learning techniques have revolutionized the early identification of lung disorders. We expect that this work will equip medical professionals with the awareness they require in order to recognize and classify certain medical disorders.

Awake spinal surgery: simplifying the learning curve with a patient selection algorithm.

OBJECTIVE: There is a learning curve for surgeons performing "awake" spinal surgery. No comprehensive guidelines have been proposed for the selection of ideal candidates for awake spinal fusion or decompression. The authors sought to formulate an algorithm to aid in patient selection for surgeons who are in the startup phase of awake spinal surgery. METHODS: The authors developed an algorithm for selecting patients appropriate for awake spinal fusion or decompression using spinal anesthesia supplemented with mild sedation and local analgesia. The anesthetic protocol that was used has previously been reported in the literature. This algorithm was formulated based on a multidisciplinary team meeting and used in the first 15 patients who underwent awake lumbar surgery at a single institution. RESULTS: A total of 15 patients who underwent decompression or lumbar fusion using the awake protocol were reviewed. The mean patient age was 61 ± 12 years, with a median BMI of 25.3 (IQR 2.7) and a mean Charlson Comorbidity Index of 2.1 ± 1.7; 7 patients (47%) were female. Key patient inclusion criteria were no history of anxiety, 1 to 2 levels of lumbar pathology, moderate stenosis and/or grade I spondylolisthesis, and no prior lumbar surgery at the level where the needle is introduced for anesthesia. Key exclusion criteria included severe and critical central canal stenosis or patients who did not meet the inclusion criteria. Using the novel algorithm, 14 patients (93%) successfully underwent awake spinal surgery without conversion to general anesthesia. One patient (7%) was converted to general anesthesia due to insufficient analgesia from spinal anesthesia. Overall, 93% (n = 14) of the patients were assessed as American Society of Anesthesiologists class II, with 1 patient (7%) as class III. The mean operative time was 115 minutes (± 60 minutes) with a mean estimated blood loss of 46 ± 39 mL. The median hospital length of stay was 1.3 days (IQR 0.1 days). No patients developed postoperative complications and only 1 patient (7%) required reoperation. The mean Oswestry Disability Index score decreased following operative intervention by 5.1 ± 10.8. CONCLUSIONS: The authors propose an easy-to-use patient selection algorithm with the aim of assisting surgeons with patient selection for awake spinal surgery while considering BMI, patient anxiety, levels of surgery, and the extent of stenosis. The algorithm is specifically intended to assist surgeons who are in the learning curve of their first awake spinal surgery cases.

Consensus-based perioperative protocols during the COVID-19 pandemic.

OBJECTIVE: During the COVID-19 pandemic, quaternary-care facilities continue to provide care for patients in need of urgent and emergent invasive procedures. Perioperative protocols are needed to streamline care for these patients notwithstanding capacity and resource constraints. METHODS: A multidisciplinary panel was assembled at the University of California, San Francisco, with 26 leaders across 10 academic departments, including 7 department chairpersons, the chief medical officer, the chief operating officer, infection control officers, nursing leaders, and resident house staff champions. An epidemiologist, an ethicist, and a statistician were also consulted. A modified two-round, blinded Delphi method based on 18 agree/disagree statements was used to build consensus. Significant disagreement for each statement was tested using a one-sided exact binomial test against an expected outcome of 95% consensus using a significance threshold of p < 0.05. Final triage protocols were developed with unblinded group-level discussion. RESULTS: Overall, 15 of 18 statements achieved consensus in the first round of the Delphi method; the 3 statements with significant disagreement (p < 0.01) were modified and iteratively resubmitted to the expert panel to achieve consensus. Consensus-based protocols were developed using unblinded multidisciplinary panel discussions. The final algorithms 1) quantified outbreak level, 2) triaged patients based on acuity, 3) provided a checklist for urgent/emergent invasive procedures, and 4) created a novel scoring system for the allocation of personal protective equipment. In particular, the authors modified the American College of Surgeons three-tiered triage system to incorporate more urgent cases, as are often encountered in neurosurgery and spine surgery. CONCLUSIONS: Urgent and emergent invasive procedures need to be performed during the COVID-19 pandemic. The consensus-based protocols in this study may assist healthcare providers to optimize perioperative care during the pandemic.

Neuroanesthesia Guidelines for Optimizing Transcranial Motor Evoked Potential Neuromonitoring During Deformity and Complex Spinal Surgery: A Delphi Consensus Study.

STUDY DESIGN: Expert opinion-modified Delphi study. OBJECTIVE: We used a modified Delphi approach to obtain consensus among leading spinal deformity surgeons and their neuroanesthesiology teams regarding optimal practices for obtaining reliable motor evoked potential (MEP) signals. SUMMARY OF BACKGROUND DATA: Intraoperative neurophysiological monitoring of transcranial MEPs provides the best method for assessing spinal cord integrity during complex spinal surgeries. MEPs are affected by pharmacological and physiological parameters. It is the responsibility of the spine surgeon and neuroanesthesia team to understand how they can best maintain high-quality MEP signals throughout surgery. Nevertheless, varying approaches to neuroanesthesia are seen in clinical practice. METHODS: We identified 19 international expert spinal deformity treatment teams. A modified Delphi process with two rounds of surveying was performed. Greater than 50% agreement on the final statements was considered "agreement"; >75% agreement was considered "consensus." RESULTS: Anesthesia regimens and protocols were obtained from the expert centers. There was a large amount of variability among centers. Two rounds of consensus surveying were performed, and all centers participated in both rounds of surveying. Consensus was obtained for 12 of 15 statements, and majority agreement was obtained for two of the remaining statements. Total intravenous anesthesia was identified as the preferred method of maintenance, with few centers allowing for low mean alveolar concentration of inhaled anesthetic. Most centers advocated for <150 µg/kg/min of propofol with titration to the lowest dose that maintains appropriate anesthesia depth based on awareness monitoring. Use of adjuvant intravenous anesthetics, including ketamine, low-dose dexmedetomidine, and lidocaine, may help to reduce propofol requirements without negatively effecting MEP signals. CONCLUSION: Spine surgeons and neuroanesthesia teams should be familiar with methods for optimizing MEPs during deformity and complex spinal cases. Although variability in practices exists, there is consensus among international spinal deformity treatment centers regarding best practices. LEVEL OF EVIDENCE: 5.

Safe and successful resection of difficult GI lesions using a novel single-step full-thickness resection device (FTRD®).

BACKGROUND AND STUDY AIMS: Classic endoscopic resection techniques (EMR and ESD) are limited to mucosal lesions. In the case of deeper growth into the gut wall and anatomic sites prone to perforation, the novel full-thickness resection device (FTRD®) opens a new dimension of possibilities for endoscopic resection. PATIENTS AND METHODS: Sixty patients underwent endoscopic full-thickness resection (eFTR) at our institution. Safety, learning curve, R0 resection rate, and clinical outcome were studied. RESULTS: In 97% (58/60) of the interventions, the FTRD®-mounted endoscope reached the previously marked lesion and eFTR was performed (technical success). Full-thickness resection was achieved in 88% of the cases, with an R0 resection on histological examination in 79%. The clinical success rate based on follow-up histology was even higher (88%). Adverse events occurred in 7%. Appendicitis of the residual cecal appendix after eFTR of an adenoma arising in the appendix led to the only post-eFTR surgery (1/58, 2%). Minor bleeding at the eFTR site (2/58, 3%) and an eFTR performed accidently without proper prior deployment of the OTSC® (1/58, 2%) were successfully treated endoscopically. There was no secondary perforation or eFTR-associated mortality. CONCLUSIONS: After specific training, eFTR is a feasible, safe, and promising all-in-one endoscopic resection technique. Our data show that eFTR allows complete resection of lesions affecting layers of the gut wall beneath the mucosa with a low risk of adverse events. However, our preliminary results need to be confirmed in larger, controlled studies.

Diagnostic use of endoscopic full-thickness wall resection (eFTR)-a novel minimally invasive technique for colonic tissue sampling in patients with severe gastrointestinal motility disorders.

BACKGROUND: Complex gastrointestinal (GI) motility disorders such as chronic intestinal pseudo-obstruction (CIPO) or Hirschsprung's disease (HD) are challenging to diagnose and treat appropriately. Thorough assessment of patient history, radiographic exams, endoscopy, and motility measurements aid in diagnostic workup, yet underlying histology is the cornerstone to enable a more distinct diagnosis of neuromuscular GI disorders. Traditionally, surgical procedures have been performed to obtain specimen suitable for accurate histologic analysis. METHODS: We performed endoscopic full-thickness resection (eFTR) using a full-thickness-resection device (FTRD) under moderate propofol sedation in four patients with suspected severe neuromuscular gut disorders including CIPO. KEY RESULTS: The mean age of the four patients was 43 y (range 19-56 y). Technical and histological success providing large colonic full-thickness tissue samples of excellent quality was achieved in all four patients (success rate 100%). The mean procedure time was 12 min (range 5-20 min). The mean diameter of the resected specimen was 21 mm (range 20-22 mm). No adverse events connected to the procedure itself occurred. Histology ranged from aganglionosis such as Hirschsprung's disease (HD) to hypoganglionosis and eosinophilic leiomyositis combined with lymphocytic ganglionitis in a third patient. Histology was unspecific in one patient. CONCLUSION AND INFERENCES: EFTR allows safe and minimal invasive harvesting of ample full-thickness tissue samples for accurate histological analysis in patients with suspicion of neuromuscular gut disorders.

Establishment of Over-The-Scope-Clips (OTSC®) in daily endoscopic routine.

BACKGROUND: Alongside the evolution of interventional endoscopy, the need for a more sophisticated closure tool tailored to the treatment of new challenging indications has been increasing rapidly. METHODS: We here present our collected data on 262 Over-The-Scope-Clip (OTSC®) placements in a total of 233 interventions at our institution. Follow-up was focused on clinically lasting success with regards to different indications. RESULTS: Immediate success of OTSC® treatment was observed in 87.1% of all sessions (203/233). The success rates per indication were as follows: spontaneous bleeding 84.8% (28/33); iatrogenic bleeding 100% (20/20); acute perforation 90.3% (65/72); prophylaxis for perforation 100% (24/24); anastomotic leakage 61.1% (11/18); fistulae 80.7% (46/57); diameter reduction of the gastrojejunal anastomosis 100% (6/6); and stent fixation 100% (3/3). At 30-day follow-up, the overall success rate was 67.4% (157/233). The success rates per indication were as follows: spontaneous bleeding 69.7% (23/33); iatrogenic bleeding 90% (18/20); acute perforation 86.1% (62/72); prophylaxis for perforation 100% (24/24); anastomotic leakage 33.3% (6/18); fistulae 29.8% (17/57), diameter reduction of the gastrojejunal anastomosis 83.3% (5/6); and stent fixation 66% (2/3). CONCLUSIONS: Our cohort confirms previous data on the clinical usefulness of the OTSC® in daily routine practice.

Review article including treatment algorithm: endoscopic treatment of luminal complications after bariatric surgery.

The worldwide number of performed bariatric surgeries is increasing continuously, whereas laparoscopic Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy are conducted most frequently. Alongside with the usual post-operative and metabolic complications, luminal complications such as anastomotic bleeding, ulceration, leakage, fistula formation, enlargement and stenosis of the anastomosis may occur. Evolution of interventional endoscopy frequently allows endoscopic management of complications, avoiding surgical interventions in most cases. Here, we review the various luminal complications after bariatric surgery with a focus on their endoscopic management.

The design, development, and implementation of a checklist for intraoperative neuromonitoring changes.

OBJECT: The purpose of this study was to provide an evidence-based algorithm for the design, development, and implementation of a new checklist for the response to an intraoperative neuromonitoring alert during spine surgery. METHODS: The aviation and surgical literature was surveyed for evidence of successful checklist design, development, and implementation. The limitations of checklists and the barriers to their implementation were reviewed. Based on this review, an algorithm for neurosurgical checklist creation and implementation was developed. Using this algorithm, a multidisciplinary team surveyed the literature for the best practices for how to respond to an intraoperative neuromonitoring alert. All stakeholders then reviewed the evidence and came to consensus regarding items for inclusion in the checklist. RESULTS: A checklist for responding to an intraoperative neuromonitoring alert was devised. It highlights the specific roles of the anesthesiologist, surgeon, and neuromonitoring personnel and encourages communication between teams. It focuses on the items critical for identifying and correcting reversible causes of neuromonitoring alerts. Following initial design, the checklist draft was reviewed and amended with stakeholder input. The checklist was then evaluated in a small-scale trial and revised based on usability and feasibility. CONCLUSIONS: The authors have developed an evidence-based algorithm for the design, development, and implementation of checklists in neurosurgery and have used this algorithm to devise a checklist for responding to intraoperative neuromonitoring alerts in spine surgery.

Nuances of occipitocervical fixation.

OBJECTIVE: To describe the indications and techniques for occipitocervical (OC) fixation. METHODS: The operative nuances of current OC fixation techniques are described. A surgical technique video is included. RESULTS: Pertinent literature is reviewed regarding OC fixation techniques. CONCLUSION: OC fixation systems have evolved from wire and cable techniques to plates, rods, and screws. Screw-rod constructs are easy to implant and biomechanically more rigid than wire techniques.

C1 lateral mass fixation: a comparison of constructs.

OBJECTIVE: We review our experience and technique for C1 lateral mass screw fixation. We compare the results of 3 different constructs incorporating C1 lateral mass screws: occipitocervical (OC) constructs, C1-C2 constructs, and C1 to mid/low cervical constructs. METHODS: We performed a retrospective chart review of 42 consecutive patients who underwent C1 lateral mass fixation by 2 of the authors (PVM and DC). The patient population consisted of 24 men and 18 women with a mean age of 64 years. Twenty-two patients had C1-C2 constructs. Twelve patients had constructs that started at C1 and extended to the mid/low cervical spine (one extended to T1). Eight patients underwent OC fusions incorporating C1 screws (2 of which were OC-thoracic constructs). All constructs were combined either with a C2 pars screw (38 patients), C2 translaminar screw (1 patient), or C3 lateral mass screw (3 patients). No C2 pedicle screws were used. Fusion was assessed using flexion-extension x-rays in all patients and computed tomographic scans in selected cases. Clinical outcomes were assessed with preoperative and postoperative visual analog scale neck pain scores and Nurick grading. The nuances of the surgical technique are reviewed, and a surgical video is included. RESULTS: Two patients (5%) were lost to follow-up. The mean follow-up for the remaining patients was 2 years. During the follow-up period, there were 4 deaths (none of which were related to the surgery). For patients with follow-up, the visual analog scale neck pain score improved a mean of 3 points after surgery (P < .001). For patients with myelopathy, the Nurick score improved by a mean of 1 grade after surgery (P < .001). The postoperative complication rate was 12%. The complication rate was 38% in OC constructs, 17% in C1 to mid/low cervical constructs, and 0% for C1-C2 construct cases. Patients with OC constructs had the statistically highest rate of complications (P < .001). Patients with C1 to mid/low cervical constructs had more complications than those with C1-C2 constructs (P < .001). Of the 42 cases, there were 3 pseudoarthroses (1 in an OC case, 1 in a C1 to midcervical construct, and 1 in a C1-C2 construct). OC constructs had the highest risk of pseudoarthrosis (13%) (P < .001). CONCLUSION: Patients treated with C1 lateral mass fixation constructs have a high fusion rate, reduced neck pain, and improved neurologic function. Constructs using C1 lateral mass screws do not need to incorporate C2 pedicle screws. Constructs incorporating C1 lateral mass screws are effective when combined with C2 pars screws, C2 translaminar screws, and C3 lateral mass screws. Constructs using C1 screws are associated with a higher complication rate and a higher pseudoarthrosis rate if extended cranially to the occiput or if extended caudally below C2.

Changes of circulating antibody levels induced by ABO antibody adsorption for ABO-incompatible kidney transplantation.

ABO-incompatible kidney transplantation using immunoadsorption to remove anti-A/B antibodies has become a successful clinical practice. Since the data on the specificity of the ABO columns are controversial, the present study assessed the efficiency and specificity of the ABO immunoadsorption, the effect on total immunoglobulins and antibodies previously induced by vaccination. Anti-A/B antibodies were measured by agglutination and ABO flow cytometry, total IgG/IgM, carbohydrate- and protein-specific antibodies by nephelometry and ELISA. The first immunoadsorption not only efficiently reduced donor-specific anti-A/B IgM (81%) and IgG (56%) but also reduced compatible anti-A/B IgM (59%) and IgG (34%). The measurements of antidonor A/B antibodies by direct agglutination (IgM) or flow cytometry better represented the effective antibody levels than the indirect agglutination test (IgG). The median reduction of total IgM and total IgG levels after a single immunoadsorption was 34% and 18%, respectively. Antibodies against pneumococcus and haemophilus polysaccharide antigens were significantly reduced, whereas antitetanus and antidiphtheria protein antibodies were not affected. Intravenous immunoglobulin administration restored the protective anticarbohydrate antibody levels. In summary, immunoadsorption efficiently removed antidonor A/B antibodies, but was not specific for A/B antigens. Anti-A/B antibody levels as determined by ABO flow cytometry are useful to establish the minimal number of immunoadsorptions needed for successful ABO-incompatible transplantation.

Pedicle subtraction osteotomy.

OBJECTIVE: Pedicle subtraction osteotomy (PSO) is an effective tool for the correction of fixed sagittal plane deformity. However, there is potentially significant perioperative morbidity associated with this technique. We report our perioperative morbidity rate in recently performed PSO cases treated with our present surgical, anesthetic, and monitoring techniques and discuss complication-avoidance strategies. METHODS: We conducted a retrospective study of 10 patients (mean age, 56 yr; range, 7-77 yr) undergoing thoracolumbar PSO at a single institution in the past 3 years. Two patients underwent PSO at T12, seven patients underwent PSO at L3, and one patient underwent PSO at L2. Eight of the patients had undergone at least one previous spine surgery in the region of the PSO, and nine of the patients had comorbidities that increased their surgical risk stratification. We identified all causes of perioperative morbidity. RESULTS: We classified perioperative complications into two categories: intraoperative and early postoperative. Intraoperative complications included dural tears in two patients, cardiovascular instability in one patient, and coagulopathy in two patients. Early postoperative complications included neurological deficit (one patient), wound infection (two patients), urinary tract infection (one patient), and delirium (two patients). All patients recovered fully from these complications. There was no mortality in this series. CONCLUSION: In this series, most patients undergoing PSO had multiple previous spine surgeries and comorbidities. The risk of perioperative morbidity for revision cases undergoing PSO was in excess of 50%. We discuss complication-avoidance strategies.

Cervicothoracic kyphosis.

Cervicothoracic kyphotic deformity may inhibit horizontal gaze function, impede activities of daily living, and induce disabling pain. Eventually, some patients develop a chin-on-chest deformity that limits their ability to eat and drink; in the end stage, a few patients also may have difficulty breathing. Progressive kyphosis can stretch the spinal cord leading to myelopathy with progressive lower extremity spasticity and weakness. Indications for surgery include myelopathy, pain, dysphagia or dyspnea owing to kyphosis, and difficulty maintaining a functional horizontal gaze. Patients with unstable cervicothoracic fractures also require surgical fixation. For these patients, surgical goals include deformity correction with restoration of an acceptable forward gaze, re-establishment of sagittal balance, decompression of the spinal cord (if myelopathic), and stable fixation.

Na+ currents in vestibular type I and type II hair cells of the embryo and adult chicken.

In birds, type I and type II hair cells differentiate before birth. Here we describe that chick hair cells, from the semicircular canals, begin expressing a voltage-dependent Na current (INa) from embryonic day 14 (E14) and continue to express the current up to hatching (E21). During this period, INa was present in most (31/43) type I hair cells irrespective of their position in the crista, in most type II hair cells located far from the planum semilunatum (48/63), but only occasionally in type II hair cells close to the planum semilunatum (2/35). INa activated close to -60 mV, showed fast time- and voltage-dependent activation and inactivation, and was completely, and reversibly, blocked by submicromolar concentrations of tetrodotoxin (Kd = 17 nM). One peculiar property of INa concerns its steady-state inactivation, which is complete at -60 mV (half-inactivating voltage = -96 mV). INa was found in type I and type II hair cells from the adult chicken as well, where it had similar, although possibly not identical, properties and regional distribution. Current-clamp experiments showed that INa could contribute to the voltage response provided that the cell membrane was depolarized from holding potentials more negative than -80 mV. When recruited, INa produced a significant acceleration of the cell membrane depolarization, which occasionally elicited a large rapid depolarization followed by a rapid repolarization (action-potential-like response). Possible physiological roles for INa in the embryo and adult chicken are discussed.

Cervical osteotomy for the correction of chin-on-chest deformity in ankylosing spondylitis. Technical note.

The correction of chin-on-chest deformity is challenging and requires combined anterior and posterior approaches to the cervical spine. The authors describe a cervical osteotomy technique for the correction of chin-on-chest deformity in patients with ankylosing spondylitis (AS). This procedure can be accomplished using a posterior screw rod construct combined with an anterior hybrid plate system. In patients with AS, a "front-back-front" approach may be necessary because of the deformity's rigidity. The authors describe the complicated intubation and anesthetic requirements for this approach. They performed an anterior discectomy, cervical osteotomy, and unilateral pediculectomy but did not place anterior instrumentation. Via a posterior approach, laminectomies, facetectomies, and the contralateral pediculectomy were then undertaken. A posterior cervical screw/rod system was placed and loosely connected to titanium rods. Intraoperatively the deformity was corrected by placing the neck in extension combined with compression of the posterior screws on the rods. The posterior construct is then tightened. Finally, an anterior cervical approach is performed to place a structural interbody graft and a hybrid anterior cervical plate construct. The authors have successfully used this approach to correct a chin-on-chest deformity in a patient with ankylosing spondylitis. At 1-year follow-up examination, excellent resolution of the deformity and solid fusion had been achieved. They prefer to perform this procedure by using state-of-the-art anterior and posterior instrumentation systems.

Effect of low intensity electrical stimulation on quadriceps muscle voluntary maximal strength.

BACKGROUND: Evaluate the effect of low intensity electrical stimulation (ES) training on strength. We purposefully used a low ES stimulation intensity to have it well accepted by middle aged and low performing people. Relate strength to metabolic parameters. METHODS: Experimental design. Protocol 1: effects of 11 day low intensity ES training on quadriceps muscle maximal voluntary contraction (MVC). Protocol 2: effects of 3 day training at low intensity ES + voluntary contraction at 60% of MVC (co-contraction). VARIABLES MEASURED: maximal voluntary strength (FMAX), strength during ES (FES), strength developed during co-contraction (FES-C), oxygen consumption, heart rate. Experimental design included a basal session, a training program and controls of measured variables during and at the end of the training program. PARTICIPANTS: protocol 1: experiments were done on 13 healthy and sedentary subjects (6 males and 7 women, mean age 50.6 years). Protocol 2: experiments done on 6 healthy sedentary men (mean age 31.5 years). RESULTS: Protocol 1: FMAX increased significantly (p<0.05) to 14 and 19% at day 6 and 11, respectively. During ES, oxygen consumption increased by 20%, but no change in heart rate was observed. Protocol 2: FMAX significantly increased (about 5%) in subjects who trained with co-contraction; conversely, FMAX did not significantly increase in a control group matched for age who trained only with voluntary contractions. CONCLUSIONS: Low intensity ES in sedentary and poorly performing people increases significantly FMAX during MVC possibly via facilitatory neurogenic mechanism.

Morphological changes in the frog cerebellar cortex after unilateral section of the statoacustic nerve.

To investigate a possible role of the cerebellum in vestibular compensation that follows a lesion to the vestibular apparatus, the morphological changes of the cerebellar cortex of adult frogs following unilateral statoacustic nerve section was analyzed by means of electron microscopy starting from 3 days after the neurectomy for up to 6 months. On the ipsilateral side, massive abnormality was found in all layers at early postsurgical intervals. This involved both nerve fibers and cell bodies. Fibers often appeared condensed or vacuolated with poorly compacted myelin sheath. Cells had electronlucent and vacuolated cytoplasm to varying extent. Alterations became less conspicuous after 30 days and after 60 days altered nerve cells were no longer present. On the contralateral side, only a few Purkinje and granule cells were affected at early postsurgical stages. This may derive from the fact that, in the frog, some of the vestibular primary afferents reach contralateral cerebellar cortex. At 30 days, alterations had substantially progressed, and at 60 days they involved all the cortical layers. Fiber debris was present in the granular and molecular layers and numerous Purkinje cells were electrondense and shrunken. This lateness in alteration may be a consequence of the prolonged silence of the vestibular nucleus contralateral to the lesion. At 4 and 6 months the tissue architecture was normal.