The CT guided transoral approach: A biopsy technique for a poorly differentiated chordoma in a 5 year old

Abstract

Mass lesions presenting at the craniocervical junction often present a unique challenge due to the complex anatomic arrangement limiting access for tissue diagnosis. The transoral approach has predominantly been used for percutaneous vertebroplasty of high cervical vertebrae with limited literature describing image guided biopsy for bony lesions in this region in the pediatric patient. We describe a technique of computed tomography guided transoral biopsy of a poorly differentiated chordoma located at the C1-C2 level in a 5-year-old child, and review this diagnosis.

Keywords: CT guided; Poorly differentiated chordoma; pediatric; spine; transoral.

Figure 1. 5 year old female with poorly differentiated chordoma

FINDINGS: MRI (1(a) – 1(d)) and non-contrast CT (1(f) and 1(g)) demonstrates a poorly differed chordoma centered at the odontoid and right lateral mass of C2 in a 5 years old female patient. (a) Sagittal MRI TSE T1 and (b) T2 weighted images demonstrate an infiltrating soft tissue mass centered at C1-C2 with lifting of the tectorium (yellow circle). There is no significant mass effect or signal changes at the spinal cord or medulla. (c) Sagittal T1 MRI images post gadolinium injection demonstrate no appreciable enhancement (red circle). (d) coronal and (e) axial, T2 weighted images demonstrate the ill-defined soft tissue mass at extending to the right lateral mass of C2 (yellow arrowheads). (f) (red arrows) axial unenhanced CT again demonstrates the soft tissue mass at C1 (g) CT coronal bone reformats show associated bony erosion at the tip of the odontoid. TECHNIQUE: (A – E) Siemens MRI scanner. Magnetic strength = 1.5 Tesla. A: T1W fat sat sagittal. TR = 600 ms TE = 10 ms. Slice thickness = 3 mm. B: T2W TSE RESTORE sagittal. TR = 2600 ms TE = 118 ms. Slice thickness = 3 mm. C: Intravenous Gadovist 1.85 ml was administered. T1W post-contrast saggital TR = 600 ms TE = 11 ms. Slice thickness = 3mm. D: T2W fat sat coronal True-FSIP. TR = 5.2 ms TE = 2.6 ms. Slice thickness = 5 mm. E: T2W TSE fat sat axial. TR = 5010 ms TE = 108 ms. Slice thickness = 4 mm. F, G Siemens CT non-contrast SOMATOM Definition FLASH. C: Slice thickness =1 mm. kVp = 100, Tube current = 60 mA. Convolution Kernel: soft tissue I31s/2. D: Slice thickness =1 mm. kVp = 100, Tube current = 58 mA. Convolution Kernel: bone I70h/2.

Figure 2. 5 year old female with poorly differentiated chordoma

FINDINGS: CT guided transoral biopsy of a poorly differentiated chordoma centered at the dens in a 5 years old female patient. (a) Axial unenhanced CT guided biopsy of the C1-C2 mass. The red arrow demonstrates the biopsy needle with 2 cm throw extended into the mass. The adjacent endotracheal tube is partially visualized (yellow arrowheads) as the procedure was completed under general anesthetic with on call surgeons in house. (b) and (c) (coronal, sagittal reformats respectively) demonstrate accurate CT guided biopsy of the mass. (d) Demonstrates sagittal unenhanced soft tissue reformats with the poorly differentiated chordoma soft tissue mass (yellow arrowheads) and biopsy needle (red arrows) appropriately positioned for tissue sampling. Image (d) was taken from the second biopsy procedure the patient underwent, which was completed using the same technique as the procedure shown in Figures 2(a) – 2(c). TECHNIQUE: (A,B,C) Siemens CT non-contrast SOMATOM Definition FLASH. Slice thickness =2 mm. kVp = 80, Tube current = 142 mA. Convolution Kernel: bone I70h/2. Gantry tilt = 0. (D): CT non-contrast SOMATOM Definition FLASH. Slice thickness =1 mm. kVp = 100, Tube current = 49 mA. Convolution Kernel: bone I31s/2. Gantry tilt = 0.

Figure 3. 5 year old female with poorly differentiated chordoma

Equipment used for a transoral biopsy of a poorly differentiated chordoma centered at the dens in a 5 years old female patient. (a) Tourniquet used to secure endotracheal tube. (b) plastic straw cut to length placed in the patients mouth to displace surrounding soft tissues. (c) Tongue depressor (d) 4-French vascular sheath and coaxial dilator (Pinnacle®; Terumo, Somerset, NJ, USA) used for stable purchase of the biopsy needle (e) 18-gauge 9 cm long semiautomatic side-cut needle with a 2 cm throw length (Quick Core®; Cook Medical, Bloomington, IN, USA) biopsy system was advanced in a coaxial fashion through the vascular sheath.