Identification of Preoperative Language Tracts for Intrinsic Frontotemporal Diseases: A Pilot Reconstruction Algorithm in a Middle-Income Country.

OBJECTIVE: Diffusion tensor imaging (DTI) tractography provides useful information that can be used to optimize surgical planning and help avoid injury during subcortical dissection of eloquent tracts. The objective is to provide a safe, timely, and affordable algorithm for preoperative DTI language reconstruction for intrinsic frontotemporal diseases. METHODS: We reviewed a prospectively acquired database of preoperative DTI reconstruction for resection of left frontotemporal lesions over 3 years at Hospital de San José and Hospital Infantil Universitario San José, Fundación Universitaria de Ciencias de la Salud, Bogota, Colombia. Preoperative and postoperative clinical and radiographic features were determined from retrospective chart review. A comprehensive review of the structural and functional anatomy of the language tracts was performed. Separate reconstruction of both ventral (semantic) and dorsal (phonologic) stream pathways is described: arcuate fasciculus, superior longitudinal fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, and inferior longitudinal fasciculus. RESULTS: Between January 2015 and January 2018, 44 tumor cases were found to be resected with preoperative fiber tracking planning and neuronavigation-guided surgery. Ten patients (7 women, 3 men) aged 28-65 years underwent resection of an intrinsic frontotemporal lesion with preoperative DTI tractography reconstruction of language tracts. Eight cases (80%) were high-grade gliomas and 2 (20%) were cavernous malformations. In 5 cases (50%), the lesion was in the frontal lobe and in 5 (50%), it was in the temporal lobe. The extent of resection was classified as gross total resection (100%), subtotal resection (>90%), or partial resection (<90%). Gross total resection was achieved in 5 cases (50%), subtotal resection was achieved in 4 cases (40%), and partial resection in the remaining case (10%). Compromised tracts included superior longitudinal fasciculus in 7 (70%), inferior longitudinal fasciculus in 4 (40%), the arcuate fasciculus in 3 (30%), and uncinate fasciculus in 1 (10%). Language function was unchanged or improved in 90% of patients. New-onset postoperative language decline occurred in 1 patient, who recovered transient phonemic paraphasias 1 month after resection. The mean follow-up time was 7 months (range, 4-12 months). Residual tumors were treated with radiation and/or with chemotherapy as indicated in an outpatient setting. CONCLUSIONS: We present a safe and efficacious preoperative DTI language reconstruction algorithm that could be used as a feasible treatment strategy in a challenging subset of tumors in low- to middle-income countries.

Principios de tractografía cerebral / Principles of brain tractography

Objetivo: hacer una revisión de los principales tractos cerebrales y sus aplicaciones en las neurociencias a partir de la experiencia en la Fundación Universitaria de Ciencias de la Salud (FUCS), Bogotá D.C., Colombia. Materiales y métodos: revisión bibliográfica y utilización de imágenes con resonadores de 1.5 T o 3 T para describir las imágenes de tractografía en enfermedades del sistema nervioso central. Resultados: se muestran las características principales de la tractografía basados en casos de nuestra institución. Discusión: en la gran mayoría de patologías cerebrales no hay estudios sobre la utilidad de la tractografía. Aunque es un estudio disponible en la actualidad, es poca la información que suele obtenerse a nivel clínico, pues toma bastante tiempo el pos proceso de las imágenes y en la mayoría de centros no está protocolizada la secuencia de obtención de la reconstrucción de cada uno de los tractos por separado. Conclusiones: es posible reconstruir los principales tractos cerebrales con escáneres de 1.5 T y 3 T, identificando las vías clave del cerebro y su relación con tumores cerebrales, trauma craneoencefálico, abuso de sustancias y otras afecciones.

Objective: to present the basic mathematical, physical and radiological principles behind tractography, as well as, providing a review of the main tracts in the brain and their applications in neuroscience from the Fundación Universitaria de Ciencias de la Salud (FUCS) in Bogota D.C., Colombia experience. Materials and Methods: bibliographic review and use of a 1.5 T or 3T MR imaging system to describe tractography images in central nervous system disorders. Results: the main features of tractography are shown based on cases at our institution. Discussion: there are no identified studies on the usefulness of tractography in the vast majority of brain related pathologies. Although this procedure is currently available, clinical information is scarce, as the image-processing techniques are lengthy and in most institutions, protocols have not been determined to reconstruct each of the tracts in the brain. Conclusions: it is possible to reconstruct brain tracts using 1.5T and 3T scanners, identifying the major brain tracts and their relationship with brain tumors, cranioencephalic trauma, substance abuse and other conditions.