Intraoperative neurophysiological monitoring (IONM) is used to monitor the integrity of neuronal pathways and is necessary in neurosurgical procedures to prevent the occurrence of new onset neurodeficits. But its use and safety in pregnant cases is sparsely reported and remains to be established.[12] This case report describes the rare experience of successful intraoperative neurophysiological monitoring during pregnancy with no adverse foetal effects.
CASE REPORT
A 28-year-old lady with 26 weeks of gestation presented with headache, seizures and no focal neurological deficits. Magnetic resonance imaging (MRI) showed a right intraventricular tumour (6.2 × 4.4 × 5 cm) extending to right thalamus [Figure 1]. The patient was scheduled for right frontoparietal craniotomy and excision under general anaesthesia with the use of intraoperative neurophysiological neuromonitoring. Motor-evoked potentials (MEPs) were monitored continuously in the intraoperative period, as the tumour was close to thalamus and internal capsule. Performing MEP stimulation in the pregnant patient could induce uterine hypercontractions with a possibility of adverse effects on the foetus.
Figure 1
Magnetic resonance imaging scan showing right intraventricular tumour
Magnetic resonance imaging scan showing right intraventricular tumourAfter counselling for probable foetal loss, general anaesthesia was induced with intravenous administration of fentanyl 2 mcg/kg and propofol 2 mg/kg. Injection atracurium (0.5 mg/kg) was used to facilitate tracheal intubation. A wedge-shaped support was placed under right hip to prevent inferior vena caval compression. After tracheal intubation, injection propofol (4–5 mg/kg/hour) and injection fentanyl (1 mcg/kg/hour) infusions were started. General anaesthesia was maintained with titration of propofol and fentanyl infusions maintaining a bispectral index (BIS) values between 30 and 50. Electrocardiogram (ECG), SpO2, arterial blood pressure (BP), capnography, BIS, train of four neuromuscular monitoring, and temperature were monitored continuously. Continuous foetal heart rate monitoring was done by placing the ECHO probe in the left infraumbilical area. Cardiotocography (CTG) was placed in same location to monitor continuously foetal heart rate and uterine contractions.Medtronics NIM Eclipse system was used for intraoperative neurophysiological monitoring. Corkscrew electrodes (C3, C4 according to the 10–20 system) were placed on the scalp and paired needle electrodes were placed bilaterally in two muscle groups of both upper (deltoid and adductor pollicis brevis) and lower limbs (tibialis anterior and abductor hallucislongus). High current transcranial electrical stimulation[3] for MEPs can induce hypercontractions in the uterus. Hence, the number of MEP stimulations was limited to minimum and the lowest possible currents (150–175 volts) were used to get evoked potentials. Each time the MEP stimulation was delivered, the uterine contractions on CTG increased transiently above 50 and then dropped back [Figure 2]. Tocolytics (magnesium sulphate, isosuxprine and terbutaline) were kept on standby for possible use in case uterine hypercontractions (more than 50 contractions) occurred after discussions with the obstetric team. No significant changes in MEP amplitude were observed intraoperatively. At the end of the procedure, trachea was extubated without any new onset motor or sensory deficits. Normal foetal heart rate and viability was confirmed with continuous CTG and foetal ECHO during and after the completion of the surgical procedure.
Figure 2
Foetal CTG monitor showing foetal heart rate and uterine contractions, red arrow showing uterine contractions rising up to 50 when MEP train of stimulus was delivered
Foetal CTG monitor showing foetal heart rate and uterine contractions, red arrow showing uterine contractions rising up to 50 when MEP train of stimulus was deliveredThe surgery for tumour resection lasted for 320 minutes during which a total of 18 trains of MEPs were applied. The stimulation parameters for MEP were a pulse width of 75 μs, number of pulses applied 7, voltage of 175 V, and a train rate of 333 per second.
DISCUSSION
A multidisciplinary team approach involving neuroanaesthesiologists, neurosurgeons, and obstetricians with continuous monitoring of the foetal wellbeing by foetal heart rate, uterine contractions by CTG, intraoperative neurophysiological monitoring by MEP were useful in our case. In our case, no deleterious intraoperative or postoperative complications were seen in mother and foetus with the use of MEP monitoring. Keeping the voltage minimum for MEP, reducing number of MEP stimulation trains, monitoring of foetal heart rate and uterine tone are some of the strategies which can be considered in such cases.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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