Artery of Percheron infarct: An unusual cause for non-awakening from anesthesia.

Sir,

Delayed awakening after general anesthesia is usually attributable to causes like hypothermia, metabolic disturbances, relative or absolute over dosage of medications and anesthetics used in the peri-operative period.[1] However sometimes in clinical practice, we encounter rare causes for nonawakening after general anesthesia. Here, we describe a rare cause for nonawakening from anesthesia due to bilateral thalamic infarcts after clipping of basilar top aneurysm.

A 48-year-old male patient presented with 4 days history of swaying while walking. There was no history of headache, loss of consciousness, vomiting or seizures. No other co morbidities, on examination, patient was conscious and oriented. Contrast computed tomography (CT) scan revealed a small bleb seen at high mid brain region in posterior fossa. Digital subtraction angiography confirmed the diagnosis of basilar top aneurysm [Figure 1a]. Patient was posted for microsurgical clipping of aneurysm under general anesthesia. Patient was induced with fentanyl 150 mcg, thiopentone 250 mg and rocuronium 50 mg. Induction and intra operative period were uneventful and two clips of 9 mm standard straight and 3 mm mini straight were applied to aneurysm uneventfully. Immediately after the surgery, patient's Glasgow Coma Scale (GCS) was E1VtM5. Postoperative CT scan head showed pneumocephalus [Figure 1b] and patient was shifted to Intensive Care Unit (ICU) for elective mechanical ventilation and observation. Even after 48 hrs postoperative, the patient's sensorium did not improve and the magnetic resonance imaging (MRI) showed bilateral thalamic infarcts [Figure 1c and d] which explained the cause for nonawakening from anesthesia. Patient was managed in ICU; he was tracheotomized, weaned from ventilator and shifted out of ICU with a GCS of E2VtM5.

Figure 1

(a) Digital subtraction angiography image showing basilar tip aneurysm, (b) postoperative computed tomography scan brain showing pneumocephalus involving bilateral frontal areas, (c and d) T2-weighted flair and T2-weighted coronal image showing hyper intensities in bilateral medial thalamic region, suggesting an acute infarct of the bilateral medial thalamus (artery of Percheron infarcts)

When the preoperative consciousness is good and surgery is relatively uncomplicated with minimal handling, extubation in the operating room is ideal, thus after uncomplicated surgery, normothermic, and normovolemic patients recover uneventfully with minimal hemodynamic changes.[1] But in neurosurgery sometimes we encounter uncommon complications such as cerebral hemorrhage,[2] cortical venous thrombosis,[3] pneumocephalus, which lead to delayed awakening after surgery.

In our case, the surgery was uneventful and immediately postoperative period patient was E1VtM5 with pupils equal and reacting. Hypothermia, metabolic abnormalities, over dosage of opiods, muscle relaxants and other anesthetics were ruled out. Based on postoperative CT scan head, we suspected pneumocephalus as the cause for delayed awakening and kept the patient under observation for 48 h. However since his sensorium did not show any improvement, we did a MRI brain, which showed bilateral thalamic infarcts. The probable anatomical cause could be, involvement of artery of Percheron, which is a normal variant of thalamic perforating branches arising from P1 segment of the posterior cerebral arteries. This branch might have been blocked while clipping of the aneurysm leading to the infarct of the bilateral thalamus.[4] Though the thalamic infarcts following clipping of basilar top aneurysm has been described previously by Jin et al.,[5] but there is no description of its effect on patient's consciousness in the immediate postoperative period. This case for the first time describes thalamic infarcts as an acute cause for nonawakening of the patient immediately after the surgery.

This case demonstrates that the treating anesthetist should be aware of this entity as a cause for delayed emergence or nonawakening from anesthesia after clipping of basilar top aneurysm.