Chondrosarcoma/trigeminal neuralgia – upfront, multisession radiosurgery/postoperative radiosurgery for trigeminal neuralgia

SKULL BASE REGION	Petroclival
HISTOPATHOLOGY	Chondrosarcoma
PRIOR SURGICAL RESECTION	Biopsy only
PERTINENT LABORATORY FINDINGS	N/A

Case description

The patient is an 84-year-old female with medical history of diabetes mellitus, cardiac disease (previous acute myocardial infarction, left bundle branch block), and thyroid issues status post total thyroidectomy. She presented with right trigeminal nerve pain associated with hypoesthesia and diplopia. Computed tomography (CT) images revealed a lesion in the right skull base with erosive features. The petrous apex and clivus were both affected by the lesion, which partially protruded into the sphenoid sinus with extension into the ipsilateral cavernous sinus and a small component projecting into the right prepontine cistern. Brain magnetic resonance imaging (MRI) confirmed the presence of a large skull-base lesion, developing from the right paramedian region and extending into the pterygopalatine fossa, cavernous sinus, and right prepontine cistern ( Figure 6.28.1 ). The lesion showed slight enhancement, surrounding and displacing the carotid artery and partially extending into the right sphenoid sinus. A transnasal endoscopic biopsy of the mass in the sphenoid sinus was obtained and confirmed the diagnosis of chondrosarcoma.

The patient’s medical history precluded performing an extended surgery, and proton therapy was offered to the patient as an initial treatment option. However, she refused for social and financial reasons. Multisession stereotactic radiosurgery (SRS) was adopted as an alternative treatment strategy (25 Gy in 5 fractions) ( Figure 6.28.2 ).

Radiosurgery Machine	CyberKnife
Radiosurgery Dose (Gy)	Tumor: 25, at the 77% isodose line Trigeminal neuralgia: 60, at the 79% isodose line
Number of Fractions	Tumor: 5 Trigeminal neuralgia: 1

Critical Structure	Dose Tolerance
Brainstem	25 Gy, maximum
Oculomotor nerves (III, IV, VI)	25/27 Gy in 4/5 fractions
Trigeminal nerve	Very high tolerance; may tolerate 75 Gy in single session