Table 1.

Questionnaire.

Operative experience
How can expert surgical skills be measured?
Total number of tumor surgeries of the CNS	>50-100
	>100-200
	>200-500
	>500
Annual caseload	>10-20
	>20-50
	>50-100
	>100
The number of procedures performed for certain histologies	Gliomas yes/no
	Meningiomas yes/no
	Metastases yes/no
	Other (please specify)
The number of procedures using certain surgical adjuncts and techniques	IONM/mapping yes/no
	Awake craniotomy yes/no
	Endoscopy yes/no
	Skull base approaches yes/no
Is experience with both resections and stereotactic biopsies required?	Yes
	Resection only is enough
	Stereotactic biopsy only is enough
Experience with spinal and nerve tumors is required	Spinal tumors (extramed.) yes/no
	Spinal tumors (intramed.) yes/no
	Spinal tumors (epidural) yes/no
	Spinal fusion yes/no
	Peripheral nerve tumors yes/no
Neuro-oncology expertise includes experience with the following tumors or tumor locations	Pituitary yes/no
	Vestibular schwannoma yes/no
	Other skull base yes/no
	Pediatric yes/no
Please define the number of surgeries which define surgical expertise with a certain tumor type	Number of intrinsic brain tumors
	>50
	>100
	>200
	Other (please specify)
	Number of metastases
	>50
	>100
	>200
	Other (please specify)
	Number of meningiomas
	>50
	>100
	>200
	Other (please specify)
Other personal skills & qualifications
The following skills are necessary	Communication skills yes/no
	Team player yes/no
	Leadership yes/no
	Administrative skills
	Teaching activities yes/no
	Research background yes/no
	Other (please specify)
The following formal qualifications (at least observership/hospitation) are necessary	Medical oncology (chemotherapy) background yes/no
	Radiotherapy/-surgery yes/no
	Medical ethics background yes/no
	Medicolegal, regulations, economics yes/no
	Other (please specify)
Required continuing education: conference attendance	at least bi-annually
	≥1/yr.
	Other (please specify)
Necessary publication/research activities	No activities required
	Conference abstracts/talks
	Publications in scientific journals
Institution & workplace
The following resources are required	Specialized nursing yes/no
	Specialized OR team yes/no
	Specialized ICU (NICU) yes/no
	Specialized tumor board yes/no
	Specialized interprofessional neuro-oncology team yes/no
	More than one dedicated neuro-oncological surgeon yes/no
Interdisciplinary neuro-oncology	Expert neuro-oncological surgery services rely heavily on in-house collaborations
	Allied disciplines do not have to be in-house, but formal collaborations and an interdisciplinary tumor board are necessary
	“Stand-alone” expert neuro-oncological surgery services are possible
The optimal performance of an expert	requires working in a tertiary center
	is possible in any neurosurgical unit or department offering complete neurosurgery services and resident training
	is possible in any neurosurgical unit or department
	is possible in a (private) practice setting