Biomedical subjects

Mark P Johnson

Publications and source records attributed to Mark P Johnson.

At least 19 recordsLinked to original sources

PubMed2006

Fetal head biometry assessed by fetal magnetic resonance imaging following in utero myelomeningocele repair.

OBJECTIVE: To examine the impact of fetal myelomeningocele (MMC) repair on fetal head biometry and cerebrospinal fluid (CSF) spaces assessed by magnetic resonance imaging (MR) studies. STUDY DESIGN: Axial measurements of intracranial structures were taken at defined anatomical landmarks. Pre- and postnatal head biometry data and CSF spaces obtained from in utero repaired MMC fetuses (n = 22) were compared to the pre- and postnatal measurements of MMC patients that underwent standard neurosurgical MMC repair after birth (n = 16) and a cohort of age-matched control patients (prenatal, n = 52; postnatal, n = 9). RESULTS: In fetuses with MMC, initial MR scans showed an almost complete absence of supratentorial and posterior fossa CSF spaces. No differences in postnatal CSF spaces were found between controls and prenatally repaired MMC newborns. In fetuses with postnatal MMC repair, CSF spaces remained significantly reduced (p < 0.0001). The mean ventricular diameter (VD) increase in the postnatal repaired MMC group was significantly higher compared to the mean percentage of VD increase in the fetal repaired MMC group (6.4 vs. 4.2 mm; p = 0.02). Pre- and postnatal brain thickness measurements were significantly reduced in both MMC populations compared to age-matched normal values (p < 0.0001). In contrast to postnatally repaired patients, in utero repair fetuses showed significant reversal of hindbrain herniation and normalization of the posterior fossa CSF spaces. CONCLUSION: Mid-gestational repair of MMC promotes normalization of extra-axial CSF spaces. Due to progressive ventriculomegaly, brain thickness remains decreased in both prenatal repaired and age-matched non-repaired MMC patients when compared to age-matched normal values. Restoration of CSF volume in the posterior fossa after in utero repair is indicative of reversal of hindbrain herniation.

Brain↗

PubMed2006

Prenatal diagnosis and postnatal management of diffuse congenital hyperinsulinism: a case report.

We present the first case of the prenatal diagnosis of congenital hyperinsulinism based on the genetic analysis of known family mutations in the SUR1 gene. An amniocentesis was performed at 16 weeks gestation at which time two mutations in the SUR1 gene were identified consistent with the diagnosis of diffuse hyperinsulinism. The mother was transported to our facility and underwent an elective caesarian section at 38 weeks gestation. The diagnosis was confirmed and treatment was initiated within the first minutes of life. After a short course of failed medical management, the patient underwent a 98% pancreatectomy with subsequent good glycemic control. This case highlights the benefits of the timely in utero diagnosis of hyperinsulinism by mutational analysis.

ATP-Binding Cassette Transporters↗

PubMed2006

Cystic adenomatoid malformation of the lung: review of genetics, prenatal diagnosis, and in utero treatment.

Prenatal identification of lung abnormalities has increased with prenatal surveillance. Treatment usually requires serial ultrasound observation but in rare situations in utero therapy may be required for fetal survival. We review the genetics, prenatal evaluation, and treatment of lung abnormalities with congenital cystic adenomatoid malformation (CCAM). Other lung lesions, bronchopulmonary sequestration (BPS), hybrid lesions involving both malformations, congenital lobar emphysema (CLE), are briefly included as differential diagnosis options. Outcome of fetuses identified to have CCAM lung abnormalities resulting in fetal hydrops and having in utero therapy (thoracoamniotic shunting, fetal thoracotomy, EXIT delivery) are discussed. In the appropriate situation, this maternal fetal surgery approach for CCAM is life-saving for the affected fetus with acceptable maternal morbidity risks in the present and future pregnancies.

Cystic Adenomatoid Malformation of Lung, Congenita↗

PubMed2006

Congenital pulmonary lymphangiectasis sequence: a rare, heterogeneous, and lethal etiology for prenatal pleural effusion.

OBJECTIVE: Case report and literature review for congenital pulmonary lymphangiectasis (CPL) CASE REPORT: Male fetus with bilateral pleural effusion, thoracoamniotic shunt, preterm delivery, and prolonged neonatal course with neonatal death at 3 months. Autopsy-identified CPL. DISCUSSION: Review of pathology, clinical course, and genetics of CPL. CONCLUSION: This postnatal diagnosis of CPL/Hennekam syndrome must be considered with prenatal counseling regarding a fetus with bilateral pleural effusions. This pathological entity is autosomal recessive and has a significant risk of lethality.

Adult↗

PubMed2006

Severe pulmonary hypoplasia associated with giant cervical teratomas.

BACKGROUND: The use of the ex utero intrapartum treatment (EXIT) procedure has salvaged many fetuses with giant neck masses. Despite an adequate airway, a subset of these patients die from an inability to achieve adequate gas exchange. METHODS: We reviewed our experience with the EXIT procedure from 1996 to 2004. The EXIT was used to deliver 23 fetuses with giant neck masses. RESULTS: Three fetuses with giant cervical teratomas died of severe pulmonary hypoplasia. On postmortem, these patients had severe airway distortion by the mass. The carina was retracted superiorly to the first or second rib resulting in compression of the lungs in the apices of the chest and pulmonary hypoplasia. Hypoplasia was reflected in the lung weights of 24 vs 38 g and 17 vs 34 g for age-matched normal lung. CONCLUSIONS: Unsuspected obstructive fetal neck masses can be fatal because of an inability to secure an airway. Prenatal ultrasonography can identify fetuses at risk, allowing the fetus to be salvaged using the EXIT procedure. Despite obtaining airway control, a subset of these patients will die because of pulmonary hypoplasia. When counseling patients with large cervical masses it is important to discuss potential pulmonary hypoplasia in these patients.

Airway Obstruction↗

PubMed2006

Fetal posterior fossa volume: assessment with MR imaging.

PURPOSE: To retrospectively determine the relationship between posterior fossa volume (PFV) and estimated gestational age (EGA) and/or femur length (FL) during pregnancy for the purpose of developing a normal growth curve. MATERIALS AND METHODS: Advance institutional review board approval was obtained for this HIPAA-compliant study, and the need for parent informed consent was waived. A cross-sectional retrospective study was performed to measure PFV on in vivo magnetic resonance (MR) images obtained in 76 fetuses of 18-36 weeks gestation who had a morphologically normal CNS. Because this was a retrospective series, MR imaging techniques varied slightly, but all fetuses underwent imaging at contiguous 3-5-mm intervals in at least two orthogonal planes, with repetition time msec/echo time msec, 5-12/62-95; number of signals acquired, one; flip angle, 150 degrees -180 degrees; and matrix, 128-192 x 256. Posterior fossa areas were manually traced on half-Fourier rapid acquisition with relaxation enhancement in utero fetal MR images by one observer. PFVs were then calculated by manually summing areas from the contiguous sections and multiplying the total area by the section thickness. An average PFV (APFV) across orthogonal planes was calculated for each fetus, and the relationship between APFV and EGA was mathematically modeled. Coronal, transverse, and sagittal views were compared with correlations and Bland-Altman plots. Two additional observers repeated the measurements for a small subset of fetuses (n = 5). Paired t test analyses were also performed to determine significant differences between sagittal, transverse, and coronal measurements, as well as to determine preliminary intraobserver and interobserver variability of measurements in a subset of cases. RESULTS: The relationship between APFV (in cubic centimeters) and EGA (in weeks) was well described by a single exponential function [APFV = 0.689 exp(EGA/9.10)]. APFV doubling time was 6.31 weeks. Root-mean-square variation of values around the model line was 1.63 cm(3). There was no statistically significant intra- or interobserver variation (P > .16 for all fetuses) at preliminary analysis. No correlation between APFV and FL could be found. CONCLUSION: The normal fetal PFV growth curve generated in this study may have potential as a model for clinical application.

Cranial Fossa, Posterior↗

PubMed2006

Diagnosis and characterization of fetal sacrococcygeal teratoma with prenatal MRI.

OBJECTIVE: The purpose of this study was to determine whether prenatal MRI provides additional information about fetal sacrococcygeal teratoma compared with prenatal sonography. MATERIALS AND METHODS: Twenty-two pregnant women with fetal sacrococcygeal teratoma underwent prenatal MRI (mean gestational age, 23 weeks). The size, location, mass characteristics, and compressive effects of the tumors were determined and correlated with sonography and postnatal findings. RESULTS: Based on the MRI findings, the following American Academy of Pediatrics, Surgical Section classifications were assigned: type I in six patients, type II in 12, and type III in four. No type IV tumors were found. The sacrococcygeal teratoma appeared entirely cystic in five fetuses, microcystic in one, mixed cystic and solid in 12, and solid in four. The diagnosis of sacrococcygeal teratoma was accurate in all cases assessed at our center using both MRI and sonography. Two additional patients initially referred with the diagnosis of sacrococcygeal teratoma had a different diagnosis at reevaluation at our institution (healthy, n = 1; myelomeningocele, n = 1). MRI was superior to sonography for detecting displacement of the colon (n = 11), urinary tract dilatation (n = 9), hip dislocation (n = 4), intraspinal extension (n = 2), and vaginal dilation (n = 1). In fetuses with sacrococcygeal teratoma types II and III, MRI better showed the cephalic extent of the tumor compared with sonography. MRI findings were confirmed at surgery or autopsy in all patients. Three fetuses with high output cardiac physiology underwent open fetal resection of the tumor at 21-, 24-, and 26-weeks' gestational age with two surviving. CONCLUSION: Our results show that ultrafast fetal MRI is a useful adjunct to the prenatal evaluation of fetal sacrococcygeal teratoma. Compared with sonography, MRI more accurately characterized the intrapelvic and abdominal extent of the tumors and provided more information on compression of adjacent organs. The additional anatomic resolution provided by MRI resulted in more accurate prenatal counseling and improved preoperative planning for surgical resection.

Female↗

PubMed2005

Ascent exhalations of Antarctic fur seals: a behavioural adaptation for breath-hold diving?

Novel observations collected from video, acoustic and conductivity sensors showed that Antarctic fur seals consistently exhale during the last 50-85% of ascent from all dives (10-160 m, n > 8000 dives from 50 seals). The depth of initial bubble emission was best predicted by maximum dive depth, suggesting an underlying physical mechanism. Bubble sound intensity recorded from one seal followed predictions of a simple model based on venting expanding lung air with decreasing pressure. Comparison of air release between dives, together with lack of variation in intensity of thrusting movement during initial descent regardless of ultimate dive depth, suggested that inhaled diving lung volume was constant for all dives. The thrusting intensity in the final phase of ascent was greater for dives in which ascent exhalation began at a greater depth, suggesting an energetic cost to this behaviour, probably as a result of loss of buoyancy from reduced lung volume. These results suggest that fur seals descend with full lung air stores, and thus face the physiological consequences of pressure at depth. We suggest that these regular and predictable ascent exhalations could function to reduce the potential for a precipitous drop in blood oxygen that would result in shallow-water blackout.

Adaptation, Physiological↗

PubMed2005

Management of fetal mediastinal teratoma.

BACKGROUND/PURPOSE: Mediastinal teratomas are rare congenital germ cell tumors that prenatally can compress mediastinal structures and cause hydrops. Two possible presentations of massive fetal mediastinal teratoma include hydrops leading to fetal demise, or fetal esophageal and airway compression causing late-gestation polyhydramnios and preterm labor. The authors present 2 cases of fetal mediastinal teratoma that illustrate successful strategies for either of these presentations. METHODS: A 37-year-old woman carrying a fetus with a mediastinal mass and secondary hydrops at 23 weeks of gestation underwent in utero resection of the mass. Delivery was by cesarean delivery at 25 weeks because of preterm labor. A 24-year-old mother carrying a fetus with a mediastinal mass and severe polyhydramnios at 36 weeks of gestation underwent an ex utero intrapartum therapy procedure for establishment of an airway and tumor resection on uteroplacental support. RESULTS: These strategies resulted in physiologic improvement in the first case and controlled resection and resuscitation in the second. The first patient had significant sequelae of prematurity including bronchopulmonary dysplasia but is currently well at 9 months of age. The second patient is well at 1 year of age. CONCLUSIONS: Massive fetal mediastinal teratoma can result in fetal or neonatal mortality by a variety of mechanisms. Optimal prenatal and perinatal management is required to salvage fetuses compromised by this lesion.

Adult↗

PubMed2005

The ex utero intrapartum therapy procedure for high-risk fetal lung lesions.

BACKGROUND: Indications for the ex utero intrapartum therapy (EXIT) procedure have expanded to include any fetal anomaly in which resuscitation of the neonate may be compromised. METHODS: We reviewed the medical records of 9 patients after resection of lung lesions during the EXIT procedure. RESULTS: The mean gestational age at EXIT procedure was 35.4 weeks. All lung masses maintained large sizes late into gestation with mean mass volume/head circumference ratio of 2.5 at presentation and 2.2 at EXIT. Seven of 9 fetuses demonstrated hydropic changes (n = 6) and/or polyhydramnios (n = 5), and underwent prenatal intervention including thoracentesis, thoracoamniotic shunt placement, amnioreduction, and/or betamethasone administration. Overall survival after EXIT for lung mass resection was 89%. The average time on placental bypass was 65 minutes. Postnatal complications included reoperation for air leak (n = 1), reoperation for bleeding (n = 1), and death from sepsis and prematurity (n = 1). Venoarterial extracorporeal membrane oxygenation was used in 4 neonates for persistent pulmonary hypertension. Maternal prenatal complications included polyhydramnios (n = 5), preterm labor (n = 4), and chorioamnionitis (n = 1). One mother required perioperative blood transfusion. CONCLUSION: The EXIT procedure allows for controlled resection of large fetal lung lesions at delivery, avoiding acute respiratory decompensation related to mediastinal shift, air trapping, and compression of normal lung.

Adolescent↗

PubMed2005

Long-term outcomes in children treated by prenatal vesicoamniotic shunting for lower urinary tract obstruction.

OBJECTIVE: Limited information is available about long-term outcomes in children treated prenatally for lower urinary tract obstruction. Our aim was to evaluate outcomes in children treated in utero with vesicoamniotic shunts. METHODS: Clinical outcomes in 20 pregnancies with a singleton male fetus, oligo/anhydramnios, and lower urinary tract obstruction were studied using chart review and phone and written clinical questionnaire for parents, pediatricians, and urologists. RESULTS: Overall 1-year survival was 91%. Two neonatal deaths occurred from pulmonary hypoplasia. Mean gestational age at delivery was 34.6 weeks, mean days from shunting to delivery were 84.4, and mean birth weight was 2,574 g. Prenatal urinary prognosis was good in 13, borderline in 2, and poor in 3 of the survivors. Mean age at follow-up was 5.83 years. Posterior urethral valves were confirmed in 7 males, urethral atresia in 4, and prune belly syndrome in 7. Eight children had acceptable renal function, 4 had mild insufficiency, and 6 required dialysis and eventual renal transplant. Eleven children had normal bladder function with spontaneous voiding, 6 required catheterization, and 1 child still had a vesicostomy. Height and weight were below the 25th percentile in 9 children. Persistent respiratory problems were present in 8, musculoskeletal problems in 9, and frequent urinary tract infections were reported in 9. Health-related quality of life results in our group with lower urinary tract obstruction were similar to those in a healthy child population. CONCLUSION: Male children who underwent prenatal bladder shunting were neurodevelopmentally normal. Although one third of the surviving babies required dialysis and transplantation, the majority have acceptable renal and bladder function and report satisfactory quality of life. LEVEL OF EVIDENCE: III.

Adolescent↗

PubMed2005

Three-dimensional beam pattern of regular sperm whale clicks confirms bent-horn hypothesis.

The three-dimensional beam pattern of a sperm whale (Physeter macrocephalus) tagged in the Ligurian Sea was derived using data on regular clicks from the tag and from hydrophones towed behind a ship circling the tagged whale. The tag defined the orientation of the whale, while sightings and beamformer data were used to locate the whale with respect to the ship. The existence of a narrow, forward-directed P1 beam with source levels exceeding 210 dBpeak re: 1 microPa at 1 m is confirmed. A modeled forward-beam pattern, that matches clicks >20 degrees off-axis, predicts a directivity index of 26.7 dB and source levels of up to 229 dBpeak re: 1 microPa at 1 m. A broader backward-directed beam is produced by the P0 pulse with source levels near 200 dBpeak re: 1 microPa at 1 m and a directivity index of 7.4 dB. A low-frequency component with source levels near 190 dBpeak re: 1 microPa at 1 m is generated at the onset of the P0 pulse by air resonance. The results support the bent-horn model of sound production in sperm whales. While the sperm whale nose appears primarily adapted to produce an intense forward-directed sonar signal, less-directional click components convey information to conspecifics, and give rise to echoes from the seafloor and the surface, which may be useful for orientation during dives.

Acoustics↗

PubMed2005

Echolocation clicks of free-ranging Cuvier's beaked whales (Ziphius cavirostris).

Strandings of beaked whales of the genera Ziphius and Mesoplodon have been reported to occur in conjunction with naval sonar use. Detection of the sounds from these elusive whales could reduce the risk of exposure, but descriptions of their vocalizations are at best incomplete. This paper reports quantitative characteristics of clicks from deep-diving Cuvier's beaked whales (Ziphius cavirostris) using a unique data set. Two whales in the Ligurian Sea were simultaneously tagged with sound and orientation recording tags, and the dive tracks were reconstructed allowing for derivation of the range and relative aspect between the clicking whales. At depth, the whales produced trains of regular echolocation clicks with mean interclick intervals of 0.43 s (+/- 0.09) and 0.40 s (+/- 0.07). The clicks are frequency modulated pulses with durations of approximately 200 micros and center frequencies around 42 kHz, -10 dB bandwidths of 22 kHz, and Q(3 dB) of 4. The sound beam is narrow with an estimated directionality index of more than 25 dB, source levels up to 214 dB(pp) re: 1 microPa at 1 m, and energy flux density of 164 dB re: 1 microPa2 s. As the spectral and temporal properties are different from those of nonziphiid odontocetes the potential for passive detection is enhanced.

Animals↗

PubMed2005

Off-axis effects on the multipulse structure of sperm whale usual clicks with implications for sound production.

Sperm whales (Physeter macrocephalus) produce multipulsed clicks with their hypertrophied nasal complex. The currently accepted view of the sound generation process is based on the click structure measured directly in front of, or behind, the whale where regular interpulse intervals (IPIs) are found between successive pulses in the click. Most sperm whales, however, are recorded with the whale in an unknown orientation with respect to the hydrophone where the multipulse structure and the IPI do not conform to a regular pulse pattern. By combining far-field recordings of usual clicks with acoustic and orientation information measured by a tag on the clicking whale, we analyzed clicks from known aspects to the whale. We show that a geometric model based on the bent horn theory for sound production can explain the varying off-axis multipulse structure. Some of the sound energy that is reflected off the frontal sac radiates directly into the water creating an intermediate pulse p1/2 seen in off-axis recordings. The powerful p1 sonar pulse exits the front of the junk as predicted by the bent-horn model, showing that the junk of the sperm whale nasal complex is both anatomically and functionally homologous to the melon of smaller toothed whales.

Acoustics↗

PubMed2004

Sperm whale behaviour indicates the use of echolocation click buzzes "creaks" in prey capture.

During foraging dives, sperm whales (Physeter macrocephalus) produce long series of regular clicks at 0.5-2 s intervals interspersed with rapid-click buzzes called "creaks". Sound, depth and orientation recording Dtags were attached to 23 whales in the Ligurian Sea and Gulf of Mexico to test whether the behaviour of diving sperm whales supports the hypothesis that creaks are produced during prey capture. Sperm whales spent most of their bottom time within one or two depth bands, apparently feeding in vertically stratified prey layers. Creak rates were highest during the bottom phase: 99.8% of creaks were produced in the deepest 50% of dives, 57% in the deepest 15% of dives. Whales swam actively during the bottom phase, producing a mean of 12.5 depth inflections per dive. A mean of 32% of creaks produced during the bottom phase occurred within 10 s of an inflection (13x more than chance). Sperm whales actively altered their body orientation throughout the bottom phase with significantly increased rates of change during creaks, reflecting increased manoeuvring. Sperm whales increased their bottom foraging time when creak rates were higher. These results all strongly support the hypothesis that creaks are an echolocation signal adapted for foraging, analogous to terminal buzzes in taxonomically diverse echolocating species.

Acoustics↗

PubMed2004

Acute cardiovascular effects of fetal surgery in the human.

BACKGROUND: Prenatal surgery for congenital anomalies can prevent fetal demise or alter the course of organ development, resulting in a more favorable condition at birth. The indications for fetal surgery continue to expand, yet little is known about the acute sequelae of fetal surgery on the human cardiovascular system. METHODS AND RESULTS: Echocardiography was used to evaluate the heart before, during, and early after fetal surgery for congenital anomalies, including repair of myelomeningocele (MMC, n=51), resection of intrathoracic masses (ITM, n=15), tracheal occlusion for congenital diaphragmatic hernia (CDH, n=13), and resection of sacrococcygeal teratoma (SCT, n=4). Fetuses with MMC all had normal cardiovascular systems entering into fetal surgery, whereas those with ITM, CDH, and SCT all exhibited secondary cardiovascular sequelae of the anomaly present. At fetal surgery, heart rate increased acutely, and combined cardiac output diminished at the time of fetal incision for all groups including those with MMC, which suggests diminished stroke volume. Ventricular dysfunction and valvular dysfunction were identified in all groups, as was acute constriction of the ductus arteriosus. Fetuses with ITM and SCT had the most significant changes at surgery. CONCLUSIONS: Acute cardiovascular changes take place during fetal surgery that are likely a consequence of the physiology of the anomaly and the general effects of surgical stress, tocolytic agents, and anesthesia. Echocardiographic monitoring during fetal surgery is an important adjunct in the management of these patients.

Adult↗

PubMed2004

North Atlantic right whales (Eubalaena glacialis) ignore ships but respond to alerting stimuli.

North Atlantic right whales were extensively hunted during the whaling era and have not recovered. One of the primary factors inhibiting their recovery is anthropogenic mortality caused by ship strikes. To assess risk factors involved in ship strikes, we used a multi-sensor acoustic recording tag to measure the responses of whales to passing ships and experimentally tested their responses to controlled sound exposures, which included recordings of ship noise, the social sounds of conspecifics and a signal designed to alert the whales. The whales reacted strongly to the alert signal, they reacted mildly to the social sounds of conspecifics, but they showed no such responses to the sounds of approaching vessels as well as actual vessels. Whales responded to the alert by swimming strongly to the surface, a response likely to increase rather than decrease the risk of collision.

Acoustics↗

PubMed2004

Prenatally diagnosed giant omphaloceles: short- and long-term outcomes.

OBJECTIVES: To review prenatal findings, short- and long-term outcomes of giant omphaloceles (GO) managed at a single institution (1996-2001). METHODS: Prenatal findings and early postnatal outcomes were retrospectively reviewed. Clinical short- and long-term outcomes were analyzed in eight and five children respectively. Parents and physicians of the children were surveyed by written questionnaires about the children's subsequent health issues. (IRB 2002-2-2683). RESULTS: Seventeen pregnancies with GO were identified: Eight fetuses were live born, four ended in (terminations), two died in utero and three were lost to follow-up. Live-born fetuses had prenatal ascites, extreme levocardia and were delivered by cesarean section at a mean of 37 weeks' gestation with a mean birth weight of 2903 g. All neonates required intubation. Two infants (2/8) died within one year. Four of the six survivors had respiratory insufficiency with a mean ventilation time of 76 days. Respiratory and feeding problems complicated the early neonatal course. Long-term follow-up was available for five patients (mean age of 33.2 months). Asthma, recurrent pulmonary infections, feeding problems, gastroesophageal reflux and failure to thrive were the major problems. CONCLUSIONS: Respiratory and feeding problems were the most common neonatal and long-term medical management issues. Parents need to be counseled prenatally about the probability of multiple surgeries and long hospitalization following birth.

Adolescent↗