Parasitic rachipagus twins; report of two cases Ami Amini Navaei & Zohreh Habibi & Ehsan Moradi & Farideh Nejat
Received: 3 November 2014 / Accepted: 17 February 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Background Parasitic fetus is a kind of conjoined twin, in which one of the twins is resorbed and some parts of the body can remain attached to the other twin. In the spinal form of parasitic twin—the so-called parasitic rachipagus—an ectopic or accessory limb is attached to the back of a normal baby or only a mass of viable tissue may remain. Method Here, we report two cases of rachipagus that one had a lower extremity on her back and the other had some tissues similar to genitalia and formed bony structures on his back. Keywords Conjoined twin . Parasitic fetus . Surgical resection
Introduction Conjoined twin is a very rare developmental event of uncertain etiology. In the International Clearinghouse for Birth Defects Surveillance and Research as a multi-center worldwide research, a total number of 383 conjoined twins among 26,138,837 births were reported. The incidence was 1.47 per A. A. Navaei Department of Neurosurgery, Shariati Hospital, Tehran University of Medical Science, Tehran, Iran e-mail: [email protected] Z. Habibi : E. Moradi : F. Nejat (*) Department of Neurosurgery, Children’s Hospital Medical Center, Tehran University of Medical Science, 14155-7854 Tehran, Iran e-mail: [email protected] Z. Habibi e-mail: [email protected] E. Moradi e-mail: [email protected]
100,000 births in this survey . Conjoined twins are always joined at homologous sites, and the clinical classification is based on the most prominent site of union. There are eight recognized nomenclatures in this field, including thoracopagus (chest), omphalopagus (umbilicus), ischiopagus (hip), pygopagus (rump), rachipagus (spine), craniopagus (cranium), cephalopagus (head), and parapagus (side) . So, rachipagus is described as a twin joined dorsally at the vertebral column. Parasitic twin is defined as a twin with unidentical growth. A parasitic fetus may completely develop and connect to partner’s body. Occasionally, depending on the severity of the pathology, only a mass of viable tissue may remain [1, 2, 7]. However, conjoined twinning is very rare, and the rachipagus is even more rare [1, 2]. An ectopic or accessory limb attached to the back is an extremely rare and strange condition, and there are only a few documented cases in the worldwide literature [1–4, 7–10]. So the aim of this study is to present two patients of parasitic rachipagus with different presenting features.
Report of cases Case 1. A 10-day old girl was admitted to the hospital with a leg on her back. She was the second child of healthy unconsanguineous parents, both aged 26 years. There was no history of infertility or using any kinds of medication before and during pregnancy. All ultrasound studies had been done during pregnancy were reported as normal. She was born with cesarean section due to fetal dystocia. She was in good general condition at the time of admission. There was a mass containing hemipelvis, lower limb, forefoot, and two toes with intact skin (Fig. 1a). She underwent extensive investigations to assess the mass and potential associated anomalies. There was neither movement nor pain sensation in
Childs Nerv Syst Fig. 1 a Photograph from two different views showing mature limb containing the hip, femur, leg, and abnormal foot. The lesion is associated with two skin abnormalities as skin dimple and skin tag at pelvic level too. b Lumbar MRI confirms tethered cord
this anomalous limb. Her neurological exams including motor of four limbs, sensory, and perianal sensation were intact. Plain film (roentgenogram) of the mass showed the pelvic bone, femur, patella, fibula, and tibia associated with some bones related to the foot. Lumbar MRI confirmed the cord to be low lying and going outside the canal at the level of attachment of parasitic twin to the neonate (Fig. 1b). Urologic studies including VCUG and kidney ultrasound were intact. Cardiac examination and echocardiography were unremarkable. The mass was excised 3 days later through a posterior midline approach. The spinal cord was attached to the parasitic twin in a situation like dorsal type lipomyelomeningocele. Cord untethering was done and the dural sac was closed watertightly without any tension. Pathological examination confirmed the lower limb inside the sample which was associated with normal tissues of lung and gasterointestinal tract. Postnatal follow-up after 9 months shows a healthy infant with normal growth, development, and neurological status. Case 2. A 5-day old boy was referred to our hospital with a soft tissue mass on his back. He was the first child of healthy non-consanguineous parents aged 22 and 24 years. All ultrasound studies had been done during pregnancy, the last one at 9 months of gestational age, were reported as normal. The parents did not have any history of infertility. He was born with normal vaginal delivery. There was a lumbar mass containing something similar to scrotum and primitive penis, plus a dimple at distal part of Fig. 2 a Photograph showing abnormal soft tissue mass on infant’s back including something similar male external genitalia and wounded mass. The tissue at the left upper corner was a structure similar to miniature scapula with small glenoid fossa. b Lumbar MRI reveals tethered cord
mass associated with intact skin coverage in most parts but wounded at a corner (Fig. 2a). His neurological examinations including motor of four limbs, sensory, and perianal sensation were intact. Lumbar MRI confirmed low-lying conus with attachment to the soft tissue mass (Fig. 2b). Urologic study including VCUG and kidney ultrasound have confirmed neurogenic bladder without vesicoureteral reflux. The mass was excised and its attachment to the cord was released. It was like a transitional lipomyelomeningocele according to the pattern of cord attachment to the superficial soft tissue mass. Pathological examination confirmed lipoma, some unidentified neural tissue, bone, and chondroid tissue inside the sample. The mass contained formed bony structures similar to small scapula with glenoid fossa and rib. Follow-up evaluations after 7 years showed a healthy child with normal growth and development. His urinary problems are managed medically.
Discussion Rachipagus is an extremely rare condition which only a few documented cases have been reported in the worldwide literature The first case was described by Jones and Larkin in 1889 . There are several theories regarding the etiology of this anomaly, namely fusion and fission theories. The most widely accepted theory is fusion theory, in which embryonic discs of
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monozygotic monoamniotic twins are located in the same amniotic cavity, in the early embryonic life. At the third or fourth gestational weeks, the neural folds of the two different embryos can merge if the skin covering the neural tube gets damaged. If the two embryos develop fair and equally, two complete but conjoined fetuses arise . But, in most cases, one of the twins dies and some parts of its body can remain attached to the vertebral column of the other fetus [10, 3]. Regarding merging the neural tubes of twins at the first steps of rachipagus formation, this anomaly has close relationship with neural tube defects. Due to this embryologic basis, most reported cases of rachipagus including this report are associated with some neural tube defects like spina bifida, lipomyelomeningocele, and diastematomyelia [4, 10]. Any structure can be found in the rachipagus parasite, among which the limbs are the most frequently structure. More rarely, heart and neural tube structures can be found in the parasite. In some rachipagus cases, the glandular tissue, intestine, or anal orifice can be seen . Most reported cases are female and neurological deficits are not common at birth time . The most frequent location has been reported in lumbosacral area [1, 2]. The goal of surgery in rachipagus patristic twin should be resection of the parasite. The attachment of spinal cord to the parasitic tissue must be recognized and should be released microsurgically at a short distance from the cord. Both of our patients had attachment to the parasitic tissue in patterns like two different kinds of lipomyelomeningocele that were corrected. With precise cord untethering procedure, good outcome with satisfactory results is expected. Associated anomalies of other organ systems should be investigated during evaluation of patients with serious congenital anomalies such as rachipagus. One of our patients had neurogenic bladder in initial investigation that is controlled with medical therapy.
Considering the spinal cord attachment to parasitic tissue and the necessity of correction of this tethered cord, close postoperative follow-up is mandatory. Like other tethered cord syndromes the parents should be warned about any new neurological deficits subsequent to secondary tethering.
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