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The role of intrapartum vibroacoustic stimulation in the prediction of neonatal myasthenia gravis
1Medical Hypotheses I Medical Hypmheses (1994) 42. 129-130 Q Longman Group UK Ltd 1994
The Role of lntrapartum Vibroacoustic Stimulation in the Prediction of Neonatal Myasthenia Gravis R. ORVIETO, T. LEVY, D. PELEG and Z. BEN-RAFAEL Department of Obstetrics and Gynecology, ‘Golda’ Medical Center (Hasharon Hospital), Petah-Tiqva, 49273, Israel and Sackler School of Medicine, Tel Aviv University, Israel (Correspondence to RO at ‘Golda’ Medical Center).
Abstract - Background - The exact mechanism for the development of neonatal myasthenia gravis is unclear, and the occurrence of neonatal myasthenia gravis cannot be predicted. Case - A case of normal duration of fetal forearm extention with return to flexion in response to vibroacoustic stimulation, and the pertinent details concerning neonatal myasthenia gravis and vibroacoustic stimulation test are described. Conclusion - Inasmuch as fetal acoustic stimulation test results in a fetal reaction resembling the startle response of the newborn, we think that it will be worthwhile to perform this test antenatally in the next encountered fetuses of myasthenic mothers in order to assess its role in the prediction of neonatal myasthenia gravis.
Introduction
Myasthenia gravis is a rare acquired autoimmune disorder that is caused by acetylcoline-receptor deficiency and involves the neuromuscular endplate. Acetylcholine-receptor antibodies, typically gamma immunoglobulin, have been detected in up to 90% of myasthenic patients (1). Pregnancy does not significantly affect the course of the disease and with occasional exceptions, women with myasthenia gravis go through pregnancy and labor without difficulty (2). Although these acetylcholine-receptor IgG antibodies are transferred from the mother to her fetus, only 1219% of neonates have symptoms of neonatal myasthenia gravis (1, 3). The exact mechanism for the development of neonatal myasthenia gravis is unclear, and the occurrence of neonatal myasthenia gravis cannot be predicted by the course or severity of disease
in the mother, or by the level of her acetylcholine receptor antibodies (4). We describe a case of maternal myasthenia gravis without any neonatal complication and an antecedent reassuring intrapartum fetal ‘startle reflex’ observed by the use of real-time ultrasound, in response to vibroacoustic stimulation. Case report A 26-year-old primigravida who was admitted to our delivery room, at 38 weeks gestation in active labor with intact membranes. The pregnancy was uncomplicated except for mysthenia gravis which was successfully controlled by pyridostigmine (a cholinesterase inhibitor). Prior to delivery a vibroacoustic stimulation test was performed under real-time ultrasonografic examination, and revealed fetal ‘startle reflex’ observed by an episode of limb extention with return
Date received 3 March 1993 Date accepted 6 April 1993
129
130 to Rexion. Fetal movements were monitored by placing the transducer as such to allow visualization of the long axis of the fetal forearm. A 3 s stimulus was delivered on the maternal abdomen over the fetal head by means of a fetal acoustic stimulator (model 146 Corometrics Medical System Inc), and the duration of forearm motion response was measured. The duration of forearm motion response was 4.5 s. Epidural block was used during labor and delivery. Spontaneous vaginal delivery of a full- term boy weighing 2860 g occurred 9.5 h after admission. The baby was in good condition with Apgar scores of 9 and 10 at 1 and 5 min respectively. Physical examination immediately after birth was unremarkable and the infant was referred to the pediatricians for special surveillance. No evidences of neonatal myasthenia gravis or any other abnormalities were observed during hospitalization. The infant was discharged on the fourth day after birth. Since the issue of breast-feeding has not been completely resolved for a mother with myasthenia gravis, it was avoided in this case. Discussion Myasthenia gravis is characterized clinically by easy fatigability of voluntary muscles, particularly those of the face and extremities. Worldwide prevalence is estimated to be 40 per million and the disease afflicts twice as many women as men, with peak incidence occurring in the third decade (5, 6). The clinical course of myasthenia gravis in pregnancy is unpredictable. Approximately two-thirds of gravid myasthenic women either remain the same or improve during their pregnancy, while one-third have an exacerbation of symptoms; furthermore, the clinical course in one pregnancy does not predict that in subsequent pregnancies and therapeutic termination does not demonstrate consistent benefit in cases of first-trimester exacerbation (7-9). Transient neonatal myasthenia gravis occurs in 1219% of the offsprings of myasthenic mothers (1, 3). Symptoms which are usually manifested within hours of birth, although they may be delayed for 34 days, include a feeble cry, facial weakness, poor suckling, generalized muscle weakness, a decreased Moro reflex, and respiratory distress (10). The diagnosis of transitory neonatal myasthenia gravis is made by the presence of anti-acetylcholine receptor antibodies in the infant and temporary improvement following subcutaneous injection of cholinesterase inhibitors (3). The disorder is self-limited, with disappearance of clinical signs in about 15-20 days, and rarely the symptoms last up to 2 months. Before the widespread use of neonatal intensive care units, the mortality rate was 11% (3, 10).
MEDICALHYPOTHESES
One of the mysterious aspects of myasthenia gravis during pregnancy is the fact that most infants of myasthenic mothers do not display myasthenia gravis symptoms despite the demonstration of anti-acetylcholine receptor antibodies in their blood. The risk of neonatal myasthenia gravis is unrelated to maternal disease severity, the presence or absence of thymectomy or to acetylcholine receptor antibody titers (3, 4, 11). Since the information hitherto available cannot predict the occurrence of neonatal myasthenia, we proposed that an evoked fetal startle response resembling that of the newborn child, might help assessing fetal neurological condition and predicting neonatal myasthenia gravis. The duration of fetal forearm movement in our case was 4.5 s, with a favorable neonatal outcome concerning neonatal myasthenia. Since Divon et al (12) have found that the mean duration of forearm motion in response to a 3 s sound-vibratory stimulus is 8.2 + 2.3, it will be worthwhile to measure the duration of fetal forearm movement of the next encountered fetuses of myasthenic mothers, in order to assess the role of this test in the prediction of neonatal myasthenia gravis. References 1. Plauche W C. Myasthenia gravis. Clin Obstet Gynecol 1983; 26: 592. 2. Cunningham F G, MacDonald P C, Gant N F. Williams Obstetrics, 18th ed. Norwalk, Connecticut: Appleton Lange, 1989: 846. 3. Fennel D F, Ringel S P. Myasthenia gravis and pregnancy. Obstet Gvnecol Surv 1987; 41: 414. 4. Gutmann-L, Seybold M E. Acetylcholine receptor antibodies in absence of neonatal myasthenia gravis (letter). Arch Nemo1 1980; 37: 738. 5. Kurtzke J F. Epidemiology of myasthenia gravis. Adv Neurol 1978; 19: 545. 6. Parther R, Rajput M C. Myasthenia gravis and pregnancy. S Afr Med J 1988; 74: 127. 7. Namba T, Brown S B, Grob D. Neonatal myasthenia gravis: Report of two cases and review of the literature. Pediatrics 1970; 45: 488. 8. Noronha A. Neurologic disorders during pregnancy and the puerperium. Clin Perinatol 1985; 12: 695. 9. Giwa-Osagie 0 F, Newton J R, Larcher V. Obstetric performance of patients with myasthenia gravis. Int J Gynaecol Obstet 1981; 19: 267. 10. Giacoia G P, Azubuike K. Autoimmune disease in pregnancy: their effect on the fetus and newborn. Obstet Gynecol Surv 1991; 46: 723. 11. Eden R D, Gall S A. Myasthenia gravis and pregnancy: A reappraisal of thymectomy. Obstet Gynecol 1983; 62: 328. 12. Divon M Y, Platt L D, Cantrell C J, Smith C V, Yeh S Y, Paul R H. Evoked fetal startle response: A possible intrauterine neurological examination. Am J Obstet Gynecol 1985; 153; 454-456. 13. van Vilet M A T, Martin C B, Nijhuis J G, Prechtl H F R. Behavioural states in the fetuses of nulliparous women. Early Hum Devel 1985; 12: 121-135.
The Role of lntrapartum Vibroacoustic Stimulation in the Prediction of Neonatal Myasthenia Gravis R. ORVIETO, T. LEVY, D. PELEG and Z. BEN-RAFAEL Department of Obstetrics and Gynecology, ‘Golda’ Medical Center (Hasharon Hospital), Petah-Tiqva, 49273, Israel and Sackler School of Medicine, Tel Aviv University, Israel (Correspondence to RO at ‘Golda’ Medical Center).
Abstract - Background - The exact mechanism for the development of neonatal myasthenia gravis is unclear, and the occurrence of neonatal myasthenia gravis cannot be predicted. Case - A case of normal duration of fetal forearm extention with return to flexion in response to vibroacoustic stimulation, and the pertinent details concerning neonatal myasthenia gravis and vibroacoustic stimulation test are described. Conclusion - Inasmuch as fetal acoustic stimulation test results in a fetal reaction resembling the startle response of the newborn, we think that it will be worthwhile to perform this test antenatally in the next encountered fetuses of myasthenic mothers in order to assess its role in the prediction of neonatal myasthenia gravis.
Introduction
Myasthenia gravis is a rare acquired autoimmune disorder that is caused by acetylcoline-receptor deficiency and involves the neuromuscular endplate. Acetylcholine-receptor antibodies, typically gamma immunoglobulin, have been detected in up to 90% of myasthenic patients (1). Pregnancy does not significantly affect the course of the disease and with occasional exceptions, women with myasthenia gravis go through pregnancy and labor without difficulty (2). Although these acetylcholine-receptor IgG antibodies are transferred from the mother to her fetus, only 1219% of neonates have symptoms of neonatal myasthenia gravis (1, 3). The exact mechanism for the development of neonatal myasthenia gravis is unclear, and the occurrence of neonatal myasthenia gravis cannot be predicted by the course or severity of disease
in the mother, or by the level of her acetylcholine receptor antibodies (4). We describe a case of maternal myasthenia gravis without any neonatal complication and an antecedent reassuring intrapartum fetal ‘startle reflex’ observed by the use of real-time ultrasound, in response to vibroacoustic stimulation. Case report A 26-year-old primigravida who was admitted to our delivery room, at 38 weeks gestation in active labor with intact membranes. The pregnancy was uncomplicated except for mysthenia gravis which was successfully controlled by pyridostigmine (a cholinesterase inhibitor). Prior to delivery a vibroacoustic stimulation test was performed under real-time ultrasonografic examination, and revealed fetal ‘startle reflex’ observed by an episode of limb extention with return
Date received 3 March 1993 Date accepted 6 April 1993
129
130 to Rexion. Fetal movements were monitored by placing the transducer as such to allow visualization of the long axis of the fetal forearm. A 3 s stimulus was delivered on the maternal abdomen over the fetal head by means of a fetal acoustic stimulator (model 146 Corometrics Medical System Inc), and the duration of forearm motion response was measured. The duration of forearm motion response was 4.5 s. Epidural block was used during labor and delivery. Spontaneous vaginal delivery of a full- term boy weighing 2860 g occurred 9.5 h after admission. The baby was in good condition with Apgar scores of 9 and 10 at 1 and 5 min respectively. Physical examination immediately after birth was unremarkable and the infant was referred to the pediatricians for special surveillance. No evidences of neonatal myasthenia gravis or any other abnormalities were observed during hospitalization. The infant was discharged on the fourth day after birth. Since the issue of breast-feeding has not been completely resolved for a mother with myasthenia gravis, it was avoided in this case. Discussion Myasthenia gravis is characterized clinically by easy fatigability of voluntary muscles, particularly those of the face and extremities. Worldwide prevalence is estimated to be 40 per million and the disease afflicts twice as many women as men, with peak incidence occurring in the third decade (5, 6). The clinical course of myasthenia gravis in pregnancy is unpredictable. Approximately two-thirds of gravid myasthenic women either remain the same or improve during their pregnancy, while one-third have an exacerbation of symptoms; furthermore, the clinical course in one pregnancy does not predict that in subsequent pregnancies and therapeutic termination does not demonstrate consistent benefit in cases of first-trimester exacerbation (7-9). Transient neonatal myasthenia gravis occurs in 1219% of the offsprings of myasthenic mothers (1, 3). Symptoms which are usually manifested within hours of birth, although they may be delayed for 34 days, include a feeble cry, facial weakness, poor suckling, generalized muscle weakness, a decreased Moro reflex, and respiratory distress (10). The diagnosis of transitory neonatal myasthenia gravis is made by the presence of anti-acetylcholine receptor antibodies in the infant and temporary improvement following subcutaneous injection of cholinesterase inhibitors (3). The disorder is self-limited, with disappearance of clinical signs in about 15-20 days, and rarely the symptoms last up to 2 months. Before the widespread use of neonatal intensive care units, the mortality rate was 11% (3, 10).
MEDICALHYPOTHESES
One of the mysterious aspects of myasthenia gravis during pregnancy is the fact that most infants of myasthenic mothers do not display myasthenia gravis symptoms despite the demonstration of anti-acetylcholine receptor antibodies in their blood. The risk of neonatal myasthenia gravis is unrelated to maternal disease severity, the presence or absence of thymectomy or to acetylcholine receptor antibody titers (3, 4, 11). Since the information hitherto available cannot predict the occurrence of neonatal myasthenia, we proposed that an evoked fetal startle response resembling that of the newborn child, might help assessing fetal neurological condition and predicting neonatal myasthenia gravis. The duration of fetal forearm movement in our case was 4.5 s, with a favorable neonatal outcome concerning neonatal myasthenia. Since Divon et al (12) have found that the mean duration of forearm motion in response to a 3 s sound-vibratory stimulus is 8.2 + 2.3, it will be worthwhile to measure the duration of fetal forearm movement of the next encountered fetuses of myasthenic mothers, in order to assess the role of this test in the prediction of neonatal myasthenia gravis. References 1. Plauche W C. Myasthenia gravis. Clin Obstet Gynecol 1983; 26: 592. 2. Cunningham F G, MacDonald P C, Gant N F. Williams Obstetrics, 18th ed. Norwalk, Connecticut: Appleton Lange, 1989: 846. 3. Fennel D F, Ringel S P. Myasthenia gravis and pregnancy. Obstet Gvnecol Surv 1987; 41: 414. 4. Gutmann-L, Seybold M E. Acetylcholine receptor antibodies in absence of neonatal myasthenia gravis (letter). Arch Nemo1 1980; 37: 738. 5. Kurtzke J F. Epidemiology of myasthenia gravis. Adv Neurol 1978; 19: 545. 6. Parther R, Rajput M C. Myasthenia gravis and pregnancy. S Afr Med J 1988; 74: 127. 7. Namba T, Brown S B, Grob D. Neonatal myasthenia gravis: Report of two cases and review of the literature. Pediatrics 1970; 45: 488. 8. Noronha A. Neurologic disorders during pregnancy and the puerperium. Clin Perinatol 1985; 12: 695. 9. Giwa-Osagie 0 F, Newton J R, Larcher V. Obstetric performance of patients with myasthenia gravis. Int J Gynaecol Obstet 1981; 19: 267. 10. Giacoia G P, Azubuike K. Autoimmune disease in pregnancy: their effect on the fetus and newborn. Obstet Gynecol Surv 1991; 46: 723. 11. Eden R D, Gall S A. Myasthenia gravis and pregnancy: A reappraisal of thymectomy. Obstet Gynecol 1983; 62: 328. 12. Divon M Y, Platt L D, Cantrell C J, Smith C V, Yeh S Y, Paul R H. Evoked fetal startle response: A possible intrauterine neurological examination. Am J Obstet Gynecol 1985; 153; 454-456. 13. van Vilet M A T, Martin C B, Nijhuis J G, Prechtl H F R. Behavioural states in the fetuses of nulliparous women. Early Hum Devel 1985; 12: 121-135.