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|LETTER TO EDITOR
|Year : 2019 | Volume
| Issue : 6 | Page : 1556-1558
Neurophysiological Monitoring in Spinal Dural Arteriovenous Fistula Surgery at the Thoracic Spine: A Case Report
Emine Taskiran1, Rahşan Kemerdere2, Orkhan Alizada2, Murat Hancı2
1 Department of Neurology, Istanbul University-Cerrahpaşa, Cerrahpaşa Faculty of Medicine, Istanbul, Turkey
2 Department of Neurosurgery, Istanbul University-Cerrahpaşa, Cerrahpaşa Faculty of Medicine, Istanbul, Turkey
|Date of Web Publication||20-Dec-2019|
Dr. Emine Taskiran
Department of Neurology, Istanbul University-Cerrahpaşa, Cerrahpaşa Faculty of Medicine, 34098, Fatih, Istanbul
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Taskiran E, Kemerdere R, Alizada O, Hancı M. Neurophysiological Monitoring in Spinal Dural Arteriovenous Fistula Surgery at the Thoracic Spine: A Case Report. Neurol India 2019;67:1556-8
|How to cite this URL:|
Taskiran E, Kemerdere R, Alizada O, Hancı M. Neurophysiological Monitoring in Spinal Dural Arteriovenous Fistula Surgery at the Thoracic Spine: A Case Report. Neurol India [serial online] 2019 [cited 2020 Jan 21];67:1556-8. Available from: http://www.neurologyindia.com/text.asp?2019/67/6/1556/273640
Dural arteriovenous fistulas (dAVFs) are very rare lesions comprising the most common type of arteriovenous malformations (AVMs) in the spine. They usually present with progressive myelopathy in middle-aged adults resulting from venous congestion and hypoperfusion of the spinal cord. Thus, the diagnosis of dAVF is often delayed or even missed out due to the slow progression of symptoms. Treatment of arteriovenous fistulas (AVFs) involves occlusion of the fistula by surgery or embolization by interventional radiology. The necessity of intraoperative neurophysiological monitoring (IOM) has been reported in endovascular procedures on the spinal cord during embolization by interventional radiology,, whereas neurophysiological data on usage, feasibility, and efficacy of IOM in spinal AVFs surgery have remained limited in the literature.
A 55-year-old man presented with progressive muscle weakness in his left leg, gait disturbance, and the urge for incontinence intermittently. The patient's symptoms began 7 months ago and worsened progressively until he required a cane for walking (Aminoff and Logue scale score of disability 3). His neurological examination at admission to the hospital showed a muscle strength of 4/5 proximally and 3/5 distally in his left lower extremity. Babinski sign was positive on the left and ankle clonus was noticed bilaterally. His neurological state worsened suddenly a night before surgery. On neurophysiological exam in the morning of the surgery, the patient was found to have muscle strength of 2/5 in the proximal lower extremities, while ankle dorsiflexion and plantar flexion of the right foot was 2/5 and the left foot was 1/5.
Thoracic spinal magnetic resonance imaging showed diffuse intramedullary edema as hyperintense signal change on T2-weigthed images between the levels of T1 and T10. Serpentine veins were detected along the dorsal aspect of the spinal cord [Figure 1]. Spinal digital subtraction angiogram showed dAVF feeding from dural branches residing into neural foramen at the left T6-7 [Figure 2].
|Figure 1: (a and b) T2-weigthed magnetic resonance imaging (MRI) showing diffuse intramedullary edema as hyperintense signal change between the levels of T1 and T10. Small perimedullary flow voids due to dilated serpentine veins were detected along the dorsal aspect of the spinal cord. Axial T2-weigthed MRI showing central edema at the level of T6|
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|Figure 2: Spinal 3-D digital subtraction angiogram showed dural arteriovenous fistula feeding from dural branches residing into neural foramen at the left T6-7|
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Neurophysiological monitoring was adjusted as posterior tibial somatosensory potentials (SEPs) and muscle motor evoked potentials (mMEPs). Monitoring of the pudendal SEP and bulbocavernosus reflex (BCR) were added for this case because of the preoperative bladder deterioration and the lower thoracic involvement.
A short-acting muscle relaxant (rocuronium, 0.5 mg/kg) was used for endotracheal intubation followed by propofol (1.5–2 mg/kg for anesthesia induction and 6–10 mg/kg/h for maintenance) plus remifentanil (0.15 μg/kg/min) for total intravenous anesthesia.
Baseline recordings demonstrated that bilateral lower extremity muscle responses were recorded with 390 V transcranial electrical stimulation of the motor cortex from C1/C2. Muscle mMEPs from bilateral quadriceps femoris and tibialis anterior (TA) muscle were not recorded with the stimulation intensity up to 600 V and also facilitation methods [Figure 3]. Bilateral tibial and pudendal SEPs were recorded symmetrically [Figure 4]. BCRs which were prominent in the left anal sphincter muscle were obtained bilaterally [Figure 4]. Recordings were repeated regularly without any changes during the surgical procedure. After the cauterization of venous component of the AVF, recordings had not change suddenly. But in the following minutes, right TA muscle response was able to be obtained with increasing amplitudes in the other muscles without any hemodynamic or anesthetic changes [Figure 3].
|Figure 3: Absence of the muscle motor evoked potential from the quadriceps femoris and tibialis anterior (TA) muscle bilaterally at the baseline and appearing of response in the right TA muscle and increasing amplitudes of other responses after occlusion|
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|Figure 4: Tibial somatosensory potential and bulbocavernosus reflex responses at the baseline and after closing dura (red color is baseline)|
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The patient woke up with improved muscle strength according to the preoperative state so that muscle strengths in all lower extremity muscles were 5/5 except the left ankle dorsiflexion, which was 3/5.
In the control angiogram which was performed by left T6-7 intercostal injections, no residual filling was observed inside the AVF [Figure 5]. No postoperative complication was observed. He could walk with the aid of a walker and his dorsiflexion recovered to 4/5 in the 10-day follow-up.
|Figure 5: Postoperative control angiogram which was performed by left T6-7 intercostal injections: no residual filling was observed inside the arteriovenous fistula|
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Prognostic determiners for spinal dAVFs are still being investigated. While clinical characteristics have prognostic significance, to date no predictive value of radiological findings has been determined for spinal AVFs based on the data originated from the small sample sizes of most published series.
Regarding the clinical presentation and outcome of surgery, it is known that patients with severe neurological deficits at presentation tend to have worse post-treatment functional outcomes than those with mild or moderate pretreatment disability. On the contrary, the neurological condition of our patient deteriorated seriously in a short time before surgery whereas he had progressive motor weakness during the previous 7 months. He achieved very quick improvement after surgery with improving neurophysiological findings at the end of surgery. This may come up with the result that fast neurological worsening culminates with fast improvement after successful treatment.
Concerning neurophysiology, Ghadirpour et al. stated that IOM has predictive value for postoperative outcome in spinal AVF treated by surgery in their case series. This study reported improvement of IOM parameters after surgery in three of 12 patients with immediate postoperative recovery of motor function similar to our result.
The role of neurophysiological monitoring in the endovascular surgery was well defined that SEPs and mMEPs can be used in combination with pharmacological provocative tests in order to predict the effects of embolization. Currently, it seems that IOM does not have a role for changing the surgical management in spinal dAVF treated by surgery while it has predictive value for the postoperative outcome.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]