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The scalp block is a critical component in the anesthetic management during awake craniotomy, aiding in pin fixation and craniotomy. However, administration of the scalp block itself can cause significant discomfort due to multiple needle punctures over the highly innervated scalp. We share a case in which EMLA (eutectic mixture of local anesthetics) cream was used to effectively minimize this discomfort.

A 30-year-old male with no other known comorbidities, was diagnosed with a left parietal intra-axial space-occupying lesion underwent awake craniotomy with tumor excision under neuronavigation. Sixty minutes prior to scalp block, 2 g of EMLA cream (2.5% lidocaine + 2.5% prilocaine) corresponding to a total of 50 mg of lignocaine and 50 mg of prilocaine, was applied to five injection sites (supraorbital, supratrochlear, zygomaticotemporal, auriculotemporal, greater and lesser occipital nerves) and covered with occlusive dressings, as shown in [Fig. 1].

Fig. 1 Sites of EMLA application and scalp block injection. 1 and 2: supratrochlear and supraorbital nerves (considered as single site due to their proximity); 3, 4, 5 and 6: zygomaticotemporal, auriculotemporal, lesser occipital, and greater occipital nerves, respectively. EMLA, eutectic mixture of local anesthetics.

Important concerns associated with EMLA application include erratic absorption, the risk of local anesthetic systemic toxicity (LAST), and methemoglobinemia.[1] Given the erratic absorption of EMLA and the duration of dermal analgesia being about 60 minutes from occlusive application, the scalp block was administered after 60 minutes of EMLA application. This 60 minutes time gap was also important to reduce the risk of LAST, as toxicity depends not only on the total dose but also on peak plasma concentration. If additional doses are given before sufficient redistribution and elimination, plasma concentrations may summate, potentially exceeding the central nervous system or cardiovascular toxicity thresholds. Staggering local anesthetic (LA) doses allows partial distribution into peripheral tissues and hepatic metabolism to occur before the next dose, thereby preventing additive or supra-additive plasma peaks. Given Tmax (time elapsed from drug administration to the point at which the drug reaches its maximum plasma concentration) for lignocaine and prilocaine is approximately 30 minutes and 45 minutes, respectively, spacing EMLA application and scalp block administration by 45 to 60 minutes reduces the overlap of peak plasma concentrations and the risk of systemic toxicity.[2] Moreover, by keeping the dose of prilocaine (a component of EMLA) well below the maximum safe limit and by limiting the surface area of EMLA application to only five injection sites, the risk of methemoglobinemia was also reduced.

Premedication included intravenous fentanyl 50 µg, midazolam 1 mg, and ondansetron 6 mg. The scalp block was administered using 10 mL of 0.5% bupivacaine (2 mL per site, i.e., supraorbital, supratrochlear, zygomaticotemporal, auriculotemporal, greater and lesser occipital nerves) and 12 mL of 0.25% bupivacaine infiltrated between injection points (6 mL between supratrochlear and auriculotemporal, and 6 mL between lesser and greater occipital nerves) using a 25-gauge Quincke needle, to block superficial nerve endings, as the scalp has extensive overlap of sensory innervation. Thus, a total of 50 mg of lignocaine, 50 mg of prilocaine, and 80 mg of bupivacaine were used. The patient's weight was 70 kg and the maximum safe doses for lignocaine (LA1), prilocaine (LA2), and bupivacaine (LA3) were calculated as 350 mg, 420 mg, and 140 mg, respectively. Using the formula mentioned below,[3] the total combined toxicity fraction for all three LA used was 0.83.

(Dose of LA1/maximum safe dose of LA1 + dose of LA2/maximum safe dose of LA2 + dose of LA3/maximum safe dose of LA3) ≤ 1

By keeping the combined LA dose below toxic limits and staggering the administration of LAs over 60 minutes, the risk of LAST was further reduced. The patient tolerated the procedure well, with a visual analog scale score of 3/10, and minimal discomfort during injections. Thereafter, the Awake-Awake-Awake technique was followed for the awake craniotomy. Intraoperatively, the patient remained cooperative and hemodynamically stable and expressed satisfaction with the experience.

EMLA application in IV cannulation and arterial line insertion is well documented.[4] [5] [6] However, its role in scalp block for awake craniotomy is rarely described. By desensitizing superficial nerve endings at injection points, EMLA reduces nociceptive input and attenuates stress responses, thus improving patient comfort and cooperation during this critical phase. Given its safety profile, ease of application, and cost-effectiveness, this simple step may enhance the overall quality of anesthesia for awake craniotomy. The aim of this correspondence is to highlight the utility of EMLA in reducing nociceptive input and stress responses during scalp block, thus improving patient tolerance and overall procedural success.

Article published online:
19 March 2026

© 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/)

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