Dandy-Walker syndrome and monochorionic twins: insight into a possible etiological mechanism.

OBJECTIVE: Dandy-Walker syndrome (DWS) is a developmental malformation of the central nervous system characterized by complete or partial absence of the cerebellar vermis, the presence of a posterior fossa cyst, and ventriculomegaly. Although DWS can be seen with Mendelian and chromosomal disorders, the actual pathophysiologic mechanism responsible for the syndrome is unknown. The incidence of DWS is approximately 1-8/100,000 births. We have noted a higher than expected incidence of DWS in a population of twins referred as complicated monochorionic twins, to include twin-twin transfusion syndrome (TTTS). The purpose of this study was to assess the incidence of DWS in monochorionic twins. METHODS: The database of all patients referred with complicated monochorionic twins was queried for the diagnosis of DWS. TTTS was defined sonographically as the combined presence of a maximum vertical pocket (MVP) of >or=8 cm in the recipient and

Fetal growth after laser therapy for twin-twin transfusion syndrome.

OBJECTIVE: The objective of the study was to compare twin weight discordance and prevalence of intrauterine growth restriction (IUGR) before laser therapy and after birth in pregnancies complicated by twin-twin transfusion syndrome (TTTS). STUDY DESIGN: Women with TTTS who underwent laser therapy with dual neonatal survivors born at least 28 days after surgery were studied. Estimated fetal weight (EFW) discordance at the preoperative sonogram and birthweight (BW) discordance were calculated. Weights below gestational age-corrected 10th percentile at sonogram and at birth for each twin were designated as IUGR. RESULTS: Among 211 women studied, the mean EFW discordance measured 26.6% and mean BW discordance was 18.4%, yielding a mean 8.2% decrease in weight discordance (P < .001). Comparing IUGR diagnoses before surgery and at birth, the recipient's proportion was unchanged (9.5% vs 7.1%, P = .353), whereas the donor's proportion decreased (64.5% vs 28.9%, P < .001). CONCLUSION: Twin weight discordance and donor fetus IUGR appear to improve after laser therapy for TTTS.

In utero laser treatment of type II vasa previa.

Vasa previa, defined as fetal vessels coursing within the membranes between the presenting part and the cervix, occurs in approximately 1:2500-5000 pregnancies. Type II vasa previa consists of fetal vessels crossing over the internal os connecting a bilobed placenta or a succenturiate lobe with the main placental mass. These vessels are prone to compression during labor or may tear when membranes rupture potentially resulting in fetal exsanguination and neonatal death. This complication could be avoided altogether if the vessels could be obliterated in utero. The purpose of this communication is to report the successful in utero laser ablation of type II vasa previa at 22.5 weeks of gestation. Subsequent ruptured membranes did not result in untoward fetal consequences. Risks and benefits of this novel procedure are discussed.

Sequential selective laser photocoagulation of communicating vessels in twin-twin transfusion syndrome.

OBJECTIVE: We have previously described the selective laser photocoagulation of communicating vessels (SLPCV) technique for the treatment of twin-twin transfusion syndrome (TTTS). Because TTTS is thought to result from a net transfer of blood from the donor twin to the recipient twin, we hypothesized that lasering the arteriovenous anastomoses from the donor to the recipient (AVDRs) first (sequential SLPCV or SQLPCV) would result in an improved hemodynamic status and decreased likelihood of intrauterine fetal demise of the donor twin (IUFD-D). MATERIALS AND METHODS: The diagnosis of TTTS was made by ultrasound showing the combined presence of a maximum vertical pocket > or = 8 cm in one sac and < or =2 cm in the other in a monochorionic/diamniotic twin pregnancy. Triplet pregnancies and monoamniotic pregnancies were excluded. Severity of TTTS was assessed using the Quintero staging system. All vascular anastomoses were endoscopically identified and classified as AVDR (AV from donor to recipient), AVRD (AV from recipient to donor), arterio-arterial (AA), or veno-venous (VV). The surgical procedure was coded as SQLPCV if all AVDRs were lasered first. Outcome measures included intrauterine fetal demise and perinatal survival. RESULTS: One hundred and ninety-three TTTS patients (137 SQLPCV, 56 SLPCV) underwent surgery from May 2003 to August 2005. Gestational age at surgery or at delivery, Stage, patent anastomoses, or persistent/reverse TTTS were not different between the groups. IUFD-D was significantly lower in the SQLPCV than in the SLPCV group (7.3% vs 21.4%, respectively, p = 0.005). Dual perinatal survival was significantly higher in the SQLPCV than in the SLPCV group (73.7% vs 57.1%, respectively, p = 0.02), although the incidence of at least one survivor was not different between the groups (90.5% vs 87.5%, respectively). Logistic regression showed SQLPCV, but not placental location, operating time or number of anastomoses to be significantly associated with a decreased likelihood of IUFD-D (p = 0.007). CONCLUSION: SQLPCV is associated with a decreased likelihood of IUFD-D and an increased rate of dual survivors compared to SLPCV. SQLPCV represents both an anatomical and functional surgical approach to the laser treatment of twin-twin transfusion syndrome.

The role of laser surgery in dissecting the etiology of absent or reverse end-diastolic velocity in the umbilical artery of the donor twin in twin-twin transfusion syndrome.

OBJECTIVE: This study was undertaken to gain insight on the cause of absent or reverse end-diastolic velocity (AREDV) in the umbilical artery (UA) of the donor twin by analysis of individual placental mass and vascular anastomoses in patients with twin-twin transfusion syndrome (TTTS) treated with laser. STUDY DESIGN: TTTS patients who successfully underwent selective laser photocoagulation of communicating vessels (SLPCV), 16 and 26 weeks' gestation, with both twins born alive and complete Doppler and placental data were considered eligible for the study. Doppler examination of the UA was performed before and 24 hours after SLPCV. Abnormal UA Doppler findings were defined as persistent AREDV. Pre- and post-SLPCV UA Doppler results yielded the following 4 groups: (1) normal-normal; (2) normal-abnormal; (3) abnormal-normal; and (4) abnormal-abnormal. The types of vascular anastomoses were categorized during surgery. Individual placental territory (IPT) was defined as individual placental weight divided by total placental weight x 100. RESULTS: There were 132 cases in group 1 and no patients in group 2. AREDV resolved in 78% (28/36) of patients (group 3) and remained unchanged in 22% (8/36) (group 4). The mean IPT-donor in group 4 was significantly smaller than in group 1 (P = .015). Patients with preoperative AREDV (groups 3 and 4) were more likely to have artery-to-artery anastomoses (P = .002). However, AREDV resolved in 57% (16/28) patients without artery-to-artery anastomoses. CONCLUSION: Preoperative AREDV may result from a small IPT, placental vascular anastomoses, or both. AREDV resulting from a small IPT may have a similar cause to that of singletons, and may be inferred by lack of postoperative resolution. Resolution of AREDV after SLPCV implies the presence of an adequate IPT and removal of donor hypotension.

Surgical management of twin reversed arterial perfusion sequence.

OBJECTIVE: The purpose of this study was to review our experience in the management of twin reversed arterial perfusion sequence to derive management recommendations. STUDY DESIGN: All patients with twin reversed arterial perfusion sequence who were seen for consultation between 1993 and 2004 were studied. Criteria for umbilical cord occlusion included abdominal circumference of the twin reversed arterial perfusion fetus that was more than or equal to the pump twin, polyhydramnios (maximum vertical pocket > or = 8 cm), abnormal Doppler studies or hydrops of the pump twin, or monoamniotic twins. Various surgical and access techniques for umbilical cord occlusion were used as they were developed. RESULTS: Seventy-four patients with twin reversed arterial perfusion sequence were studied. Sixty-five patients were considered surgical candidates, of which 51 patients underwent umbilical cord occlusion attempt. The overall perinatal survival for surgical candidates who had umbilical cord occlusion was 65% (33/51 patients) versus 42.9% (6/14 patients) for the surgical candidates who did not undergo umbilical cord occlusion (P = .1). However, perinatal outcomes in surgical patients were significantly better than expectantly treated surgical candidates if the dividing membrane was not disrupted purposely (22/28 patients; 78.5%; P = .02). Surgery within the sac of the twin reversed arterial perfusion fetus was feasible in 23.5% of patients and was associated with no incidence of premature rupture of membranes, with 83% perinatal survival, and with a significantly greater gestational age at delivery (36 weeks). There were no significant differences in perinatal outcome relative to the specific surgical technique that was used. CONCLUSION: Surgical management of twin reversed arterial perfusion sequence is indicated in high-risk patients. The surgical approach and the surgical technique should be tailored to the specific clinical presentation, preferably by performing the surgery within the sac of the twin reversed arterial perfusion sequence fetus and avoiding disruption of the dividing membrane.