Adductor canal block techniques do not lead to involvement of sciatic nerve branches: a radiological cadaveric study.

INTRODUCTION: Low and high volume mid-thigh (ie, distal femoral triangle) and distal adductor canal block approaches are frequently applied for knee surgical procedures. Although these techniques aim to contain the injectate within the adductor canal, spillage into the popliteal fossa has been reported. While in theory this could improve analgesia, it might also result in motor blockade due to coverage of motor branches of the sciatic nerve. This radiological cadaveric study, therefore, investigated the incidence of coverage of sciatic nerve divisions after various adductor canal block techniques. METHODS: Eighteen fresh, unfrozen and unembalmed human cadavers were randomized to receive ultrasound-guided distal femoral triangle or distal adductor canal injections, with 2 mL or 30 mL injectate volume, on both sides (36 blocks in total). The injectate was a 1:10 dilution of contrast medium in local anesthetic. Injectate spread was assessed using whole-body CT with reconstructions in axial, sagittal and coronal planes. RESULTS: No coverage of the sciatic nerve or its main divisions was found. The contrast mixture spread to the popliteal fossa in three of 36 nerve blocks. Contrast reached the saphenous nerve after all injections, whereas the femoral nerve was always spared. CONCLUSIONS: Adductor canal block techniques are unlikely, even when using larger volumes, to block the sciatic nerve, or its main branches. Furthermore, injectate reached the popliteal fossa in a small minority of cases, yet if a clinical analgesic effect is achieved by this mechanism is still unknown.

Percutaneous radiofrequency treatment of the gasserian ganglion for trigeminal neuralgia complicated by trochlear nerve palsy: a case report.

BACKGROUND: Trigeminal neuralgia (TN) has the highest incidence of disorders causing facial pain. TN is provoked by benign stimuli, like shaving, leading to severe, short-lasting pain. Patients are initially treated using antiepileptic drugs; however, multiple invasive options are available when conservative treatment proves insufficient. Percutaneous radiofrequency treatment of the trigeminal, or gasserian, ganglion (RF-G) is a procedure regularly used in refractory patients with comorbidities. RF-G involves complex needle maneuvering to perform selective radiofrequency heat treatment of the affected divisions. We present a unique case of cranial nerve 4 (CN4) paralysis after RF-G. CASE PRESENTATION: A male patient in his 60s presented with sharp left-sided facial pain and was diagnosed with TN, attributed to the maxillary and mandibular divisions. MRI showed a vascular loop of the anterior inferior cerebellar artery without interference of the trigeminal complex. The patient opted for RF-G after inadequate conservative therapy. The procedure was performed by an experienced pain physician and guided by live fluoroscopy. The patient was discharged without problems but examined the following day for double vision. Postprocedural MRI showed enhanced signaling between the trigeminal complex and the brainstem. Palsy of CN4 was identified by a neurologist, and spontaneous recovery followed 5 months after the procedure. CONCLUSIONS: Mention of postprocedural diplopia in guidelines is brief, and the exact incidence remains unknown. Different mechanisms for cranial nerve (CN) palsy have been postulated: incorrect technique, anatomical variations, and secondary heat injury. We observed postprocedural hemorrhage and hypothesized that bleeding might be a contributing factor in injury of CNs after RF-G.