{"id":"2f1ddd9b-3dd8-45e3-a03c-c8667b206056","slug":"resection-of-dorsal-midbrain-cavernous-malformation-through-reils-lemniscal-trigone","title":"Resection of dorsal midbrain cavernous malformation through Reil’s (lemniscal) trigone","authors":["Kara A. Parikh","Mustafa Motiwala","Kaan Yagmurlu","John E. Dugan","Alexandra H. Kramer","Nickalus R. Khan"],"abstract":"Background: Cavernous malformations of the dorsal midbrain present surgical challenges due to proximity to critical structures. Case Description: We present the case of a 37-year-old female who presented with left trochlear nerve palsy, left hemibody sensory loss, and left upper and lower extremity 4/5 weakness following ventriculoperitoneal shunting at an outside hospital for treatment of a brainstem hemorrhage. Magnetic resonance imaging showed a hemorrhagic lesion, consistent with cavernous malformation, in the dorsal midbrain. Her symptomatic growing cavernous malformation and significant mass effect were the indications for operative intervention. The paramedian supracerebellar infratentorial surgical approach was selected to minimize intersection with deep venous structures. Gross total resection of the malformation was observed on operative endoscopic inspection and postoperative imaging. She was discharged home on postoperative day 3, and by 3-month follow-up, her diplopia and hemi-body sensory loss had resolved. An anatomical review of approaches for dorsal brainstem lesions and the technical considerations of utilizing the lemniscal trigone, as well as positioning, cistern magna access for cerebrospinal fluid (CSF) relief, and endoscopic inspection are included. The patient consented to the procedure and to the presentation of her images. Institutional review board approval was deemed unnecessary due to the retrospective, case-report nature of this work. Conclusion: The case highlights the utility of the paramedian supracerebellar infratentorial approach for safe, effective resection of dorsal midbrain cavernous malformations. Careful anatomical planning, endoscopic assistance, and CSF drainage strategies can optimize outcomes and minimize morbidity in this challenging anatomical region. 0:11 - Clinical presentation 0:34 - Neurological examination 0:45 - Neuro-imaging findings 1:19 - Rationale for the procedure 1:26 - Risks of the procedure and its potential benefits 1:41 - Alternatives for treatment 3:11 - Description of the setup 3:23 - Key surgical steps 3:52 - Beginning of operative demonstration 4:15 - Superior reflection of tentorium 5:12 - Pial incision over cavernous malformation 5:48 - Endoscopic inspection of resection cavity 6:39 - Disease background 7:17 - Technical considerations 7:52 - Literature review 8:04 - Clinical and imaging outcome The institutional review board has waived ethical approval for this study. The authors certify that they have obtained all appropriate patient consent. There are no conflicts of interest. The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI. https://doi.org/10.25259/SNI_550_2025 The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.","thumbnailUrl":"https://sni-digital-videos.s3.amazonaws.com/placeholders/specialty/skull-base.png","publishDate":"2025-10-31T00:00:00.000Z","doi":"10.25259/SNI_550_2025","categories":["Skull Base","Video Abstract"],"fullTextUrl":"https://surgicalneurologyint.com/wp-content/uploads/2025/10/14044/SNI-16-450.pdf"}