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Year : 2018  |  Volume : 62  |  Issue : 6  |  Page : 466-469  

Delayed emergence from anaesthesia and bilateral mydriasis following bilateral pallidotomy

Department of Neuroanaesthesiology and Critical Care, All India Institute of Medical Sciences, New Delhi, India

Date of Web Publication11-Jun-2018

Correspondence Address:
Dr. Ankur Khandelwal
Department of Neuroanaesthesiology and Critical Care, All India Institute of Medical Sciences, New Delhi - 110 029
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ija.IJA_27_18

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Pallidotomy is a surgical procedure done widely for Parkinson's disease and various dystonias refractory to medical treatment. The technique involves radiofrequency (RF) thermal coagulation of globus pallidus internus, either unilaterally or bilaterally. The technique has been shown to produce good success. However, the involvement of nearby vital structures can result in new post-operative complications. We encountered a case of delayed emergence from anaesthesia associated with bilateral mydriasis and visual field defects in a patient after bilateral RF thermal lesioning.

Keywords: Dystonic disorders, mydriasis, pallidotomy, visual field defects

How to cite this article:
Khandelwal A, Pandia MP, Lamsal R. Delayed emergence from anaesthesia and bilateral mydriasis following bilateral pallidotomy. Indian J Anaesth 2018;62:466-9

How to cite this URL:
Khandelwal A, Pandia MP, Lamsal R. Delayed emergence from anaesthesia and bilateral mydriasis following bilateral pallidotomy. Indian J Anaesth [serial online] 2018 [cited 2021 May 12];62:466-9. Available from: https://www.ijaweb.org/text.asp?2018/62/6/466/234017

   Introduction Top

Pallidotomy, involving coagulation of the globus pallidus internus (GPi), is a surgical treatment that is widely used for treating patients with medically intractable Parkinson's disease, craniocervical dystonia and generalised dystonia.[1],[2] Complications associated with pallidotomy may result from imprecise localisation of the target lesion or due to the surgical procedure itself. Hua et al. analysed the complications in 1116 patients with Parkinson's disease who underwent microelectrode-guided radiofrequency (RF) pallidotomies. It was found that patients undergoing unilateral pallidotomy or bilateral pallidotomies may develop complications as visual field deficits, weakness, fatigue, hypersomnia, drooling, dysphagia, speech disorders, hiccups, haemorrhage, seizures, apraxia, coma, infection, mental confusion and impaired memory.[3] We encountered an unusual scenario of delayed emergence from general anaesthesia including bilateral mydriasis in a patient who underwent bilateral GPi RF thermocoagulation.

   Case Report Top

A 48-year-old male patient weighing 50 kg with a diagnosis of cervical dystonia was scheduled for microelectrode-guided bilateral GPi RF thermocoagulation. Apart from mental retardation, the patient had no co-existing systemic disease. On pre-operative examination, the patient had normal sensorium and pupillary size of 2.5 mm in both eyes along with normal response (constriction) to light stimuli. He had been receiving oral tetrabenazine three times daily. In the operating room, general anaesthesia was induced with intravenous (IV) fentanyl (100 mcg) and thiopentone (200 mg). IV rocuronium (50 mg) was used for facilitation of tracheal intubation. Anaesthesia was maintained with oxygen:nitrous oxide (2:3) and sevoflurane along with infusion of rocuronium (15 mg/h) and fentanyl (50 mcg/h). Minimum alveolar concentration of sevoflurane was maintained between 0.8 and 1.0 during surgery. Surgical techniques involved the application of Leksell stereotactic frame, creation of bilateral burr holes, opening of dura, placement of microelectrodes and lesioning of bilateral GPi interna at 78°C for 60 s. Surgical and anaesthetic courses were uneventful intraoperatively. Both rocuronium and fentanyl infusions were discontinued 50 min before the completion of surgery. Sevoflurane was gradually tapered during skin closure and then switched off along with nitrous oxide at the end of surgery. The total duration of anaesthesia was about 180 min. After the return of spontaneous respiratory efforts and inspired concentration of sevoflurane achieved to zero, reversal of neuromuscular blockade was done with neostigmine (2.5 mg) combined with glycopyrrolate (0.4 mg). Although the patient had spontaneous eye opening and good respiratory efforts, he did not follow commands. Moreover, it was observed that pupils were bilaterally semi-dilated (4.5 mm) and reacted sluggishly to light stimuli [Figure 1]. The patient was however haemodynamically stable and normothermic (36.6°C). We assessed the patient for 15 min for the feasibility of extubation. However, the patient did not follow commands and thus, we shifted him to Intensive Care Unit (ICU) for elective ventilation. Blood sugar, acid-base and electrolytes were found to be within normal levels. A possible diagnosis of non-convulsive status epilepticus was made, and a loading dose of levetiracetam 1 g was administered. A computed tomography (CT) scan of the brain was done after 4 h which did not show any new onset ischaemia, haemorrhage or oedema. The patient was sedated overnight with an infusion of fentanyl 50 mcg/h. Throughout this period, our patient had spontaneous eye opening but did not follow commands. Tracheal extubation was done on the next morning (after 16 h) as the patient followed commands and had intact airway reflexes. However, the patient complained of partial blurring of vision. On examination, it was observed that the patient had predominant right homonymous hemianopia (R > L). The size of pupils in both eyes remained the same (4.5 mm). A follow-up magnetic resonance imaging (MRI) on 3rd post-operative day revealed bilateral encroachment of optic tracts (predominantly left) by the oedema generated from the RF thermal coagulation of GPi [Figure 2]. The patient was managed conservatively and was finally discharged from hospital on 14th post-operative day. At the time of discharge, the patient had improvement in vision and visual field defects. Moreover, pupil size in both eyes had resolved to 3 mm on the 14th day.
Figure 1: Bilaterally semi-dilated pupils (4.5 mm)

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Figure 2: Magnetic resonance imaging (axial scan) showing perilesional oedema encroaching bilaterally the optic tract

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   Discussion Top

In our case, though our patient had spontaneous eye opening and adequate breathing, tracheal extubation could not be done at the end of surgery because he was not awake enough to follow commands. Infusion of muscle relaxant was stopped 50 min before completion of surgery. Although we did not monitor muscle paralysis, our patient had spontaneous breathing before administering neuromuscular reversal agent which excludes the possibility of inadequate reversal of muscle paralysis. Again, the absence of respiratory depression and pupillary constriction excludes the possibility of anaesthetic overdose. Zero inspired concentration of inhalational anaesthetic at the time of reversal and the non-alteration of consciousness level in the ICU also rules out the possibility of anaesthetic cause of delayed awakening. Hypothermia, metabolic and electrolyte imbalances as probable causes for delayed awakening were also ruled out. Possible surgical causes for delayed recovery such as new onset haemorrhage, ischaemia, oedema, pneumocephalus and raised ICP were ruled out by a post-operative CT scan of the brain. Other probable surgical causes for mental confusion and hypersomnolence include non-convulsive seizure (NCS), frontal lobe haematoma (initially excluded) or encroachment of oedema to involve the thalamus as also previously reported in literature.[3],[4] In our case, we presumed NCS to be the most important contributing factor and IV levetiracetam 500 mg was started twice daily after a loading dose of 1 g in the ICU.

Unilateral or bilateral mydriasis in neurosurgical patients is an ominous sign and calls for an urgent evaluation. Characteristic features of unilateral optic tract lesion involve contralateral homonymous hemianopia, contralateral mydriasis and subtle anisocoria. In our case, bilateral mydriasis along with blurring of vision and visual field defects probably resulted from secondary injury to the bilateral optic tracts due to thermal lesioning. Studies have demonstrated that RF lesioning produces a more extensive zone of oedema than do other heating methods, because of the higher temperature around the RF lesion.[5] Previous studies have shown that the highest temperature used to produce the most ventral lesion ranges from 60°C to 80°C.[6] Given the location of a GPi lesion lateral and dorsal to the optic tract, encroachment of oedema on the optic tracts is not an uncommon phenomenon. In our case too, a post-operative MRI showed bilateral optic tract involvement, predominantly on the left side. Favre et al. reported that there is a risk (approximately 40%) of 'minor deterioration of vision', which is unlikely to interfere with daily activities.[7] There is no specific treatment and spontaneous resolution usually takes place over a period of few weeks.

Optic tract injury can also occur due to unsuccessful localisations.[3],[6] It is possible that penetration and stimulation of the optic tract during the localisation procedure with stimulations could damage the optic tract and cause visual field defects. Theoretically, maintaining a stable distance from the target to the optic tract, with microelectrode mapping, could prevent the optic fibres from being damaged. Care should also be taken when stimulating with the lesion probe to minimise the development of oxidative reduction reactions and the development of gaseous bubbles at the tip of the probe so as to prevent damage to the adjacent tissues. Vitek et al. suggested that these can be minimised using biphasic pulse pairs rather than monophasic pulses or by reducing the duration of stimulation.[8] Literature also suggests that simultaneous bilateral pallidotomy is not favourable because of the high incidence of complications. It should be unilateral, and if desired bilaterally, then it should be staged.[3]

   Conclusion Top

Pallidotomy is a widely accepted surgical procedure for refractory PD and dystonias with good success rate. However, the procedure has its own set of complications. Through our case report, we suggest that anaesthesiologists should be aware of all the perioperative complications of RF GPi thermal coagulation. A proper documentation of the pre-operative status should be made so as to avoid medicolegal issues. Again, a constant monitoring of the neurological status is warranted in the post-operative period.


Written informed consent obtained from patient's father for the purpose of reporting this case.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient's father has given consent for his son's image and other clinical information to be reported in the journal. The patient's father understands that name and initials of his son will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Alkhani A, Lozano AM. Pallidotomy for Parkinson disease: A review of contemporary literature. J Neurosurg 2001;94:43-9.  Back to cited text no. 1
Horisawa S, Goto S, Takeda N, Terashima H, Kawamata T, Taira T, et al. Bilateral pallidotomy for cervical dystonia after failed selective peripheral denervation. World Neurosurg 2016;89:728.e1-4.  Back to cited text no. 2
Hua Z, Guodong G, Qinchuan L, Yaqun Z, Qinfen W, Xuelian W, et al. Analysis of complications of radiofrequency pallidotomy. Neurosurgery 2003;52:89-99.  Back to cited text no. 3
Lang AE, Lozano AM, Montgomery E, Duff J, Tasker R, Hutchinson W, et al. Posteroventral medial pallidotomy in advanced Parkinson's disease. N Engl J Med 1997;337:1036-42.  Back to cited text no. 4
Cosman ER, Nashold BS, Ovelman-Levitt J. Theoretical aspects of radiofrequency lesions in the dorsal root entry zone. Neurosurgery 1984;15:945-50.  Back to cited text no. 5
Biousse V, Newman NJ, Carroll C, Mewes K, Vitek JL, Bakay RA, et al. Visual fields in patients with posterior GPi pallidotomy. Neurology 1998;50:258-65.  Back to cited text no. 6
Favre J, Burchiel KJ, Taha JM, Hammerstad J. Outcome of unilateral and bilateral pallidotomy for Parkinson's disease: Patient assessment. Neurosurgery 2000;46:344-53.  Back to cited text no. 7
Vitek JL, Bakay RA, Hashimoto T, Kaneoke Y, Mewes K, Zhang JY, et al. Microelectrode-guided pallidotomy: Technical approach and its application in medically intractable Parkinson's disease. J Neurosurg 1998;88:1027-43.  Back to cited text no. 8


  [Figure 1], [Figure 2]


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