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The Nexstim Navigated Brain Stimulation System (NBS System) 4 is indicated for non-invasive mapping of the primary motor cortex of the brain to its cortical gyrus. The NBS System 4 provides information that may be used in the assessment of the primary motor cortex for pre-procedural planning.

Nexstim NEXSPEECH®, when used together with the Nexstim NBS System 4, is indicated for noninvasive localization of cortical areas that do not contain essential speech function. Nexstim NEXSPEECH® provides information that may be used in pre-surgical planning in patients undergoing brain surgery. Intraoperatively, the localization information provided by NEXSPEECH® is intended to be verified by direct cortical stimulation.

The Nexstim NBS System 4 and NBS System 4 with NEXSPEECH® are not intended to be used during a surgical procedure. The Nexstim NBS System 4 and NBS System 4 with NEXSPEECH® are intended to be used by trained clinical professionals.

The NBS System 4 combines magnetic resonance imaging-based, three dimensional localization of cortical motor areas of the brain with noninvasive TMS and simultaneous electromyography measurement to locate areas of the brain that are capable of evoking muscle responses when stimulated.

NEXSPEECH® is intended to be used in conjunction with the NBS System 4 for localization and assessment of cortical areas of speech function for pre-procedural planning purposes.

Here's an analysis of the acceptance criteria and the study proving the device meets them, based on the provided text:

Acceptance Criteria and Device Performance

The provided document focuses on establishing substantial equivalence to a predicate device for the Nexstim NBS System 4 and Nexstim NBS System 4 with NEXSPEECH®. The "acceptance criteria" are primarily demonstrated through conformance to various standards and the clinical study for NEXSPEECH®.

The primary "acceptance criteria" for NEXSPEECH® as a standalone function is its effectiveness in non-invasive localization of cortical areas that do not contain essential speech function, specifically assessed by its ability to identify negative language areas that are unlikely to show a response to direct cortical stimulation (DCS).

Table of Acceptance Criteria and Reported Device Performance (NEXSPEECH®-specific)

Study Details

2. Sample size used for the test set and the data provenance:

• Test Set Sample Size: 20 patients (age 25-70, 10 females).
• Data Provenance: Retrospective and prospective. The pre-operative Nexstim NBS with NEXSPEECH® mapping was conducted, and then compared to intraoperative DCS data from the same patients. The patients were recruited at departments of neurosurgery at 2 university hospitals (country of origin not explicitly stated, but Nexstim Oy is based in Helsinki, Finland).

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

• Ground Truth Establishment: The ground truth was established by "intraoperative language mapping performed utilizing an object naming task and a simultaneous direct electrical stimulation of the exposed cortex to identify essential language areas." The DCS was performed "according to the normal clinical practice used at each study site" by neurosurgeons.
• Number of Experts: Not explicitly stated, but it would involve at least the neurosurgeon(s) performing the DCS and potentially other clinical staff involved in the awake surgery and assessment.
• Qualifications of Experts: Neurosurgeons performing Direct Cortical Stimulation (DCS). Specific experience levels are not detailed, but it's implied they are trained clinical professionals at university hospitals.

4. Adjudication method for the test set:

• The text describes a "quantitative and qualitative analysis" comparing the locations of positive or negative language responses from NEXSPEECH® to those from DCS. There's no explicit mention of an adjudication panel for discrepant cases or a specific adjudication method like 2+1. The comparison appears to be direct between the two mapping methods.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, if so, what was the effect size of how much human readers improve with AI vs without AI assistance:

• A classic MRMC comparative effectiveness study, where human readers evaluate cases with and without AI assistance to measure improvement, was not performed for NEXSPEECH®.
• The study compared the device's output (NEXSPEECH® mapping) directly against an invasive gold standard (DCS), not against human interpretation of data with and without AI assistance. The device itself provides the "pre-procedural planning information," it doesn't assist a human reader in interpreting separate data.

6. If a standalone (i.e. algorithm only without human-in-the loop performance) was done:

• Yes, a standalone clinical study was performed for NEXSPEECH®. The study directly assessed the performance of the NEXSPEECH® module in localizing cortical areas relative to Direct Cortical Stimulation (DCS), which is considered the gold standard. The device generates the mapping information itself. The output of the NEXSPEECH® system (localization of speech areas) was compared to the output of DCS.

7. The type of ground truth used:

• Expert Consensus / Gold Standard (Pathology/Clinical Outcomes): The primary ground truth for the NEXSPEECH® effectiveness study was Direct Cortical Stimulation (DCS) performed during awake surgery. DCS is considered the "gold standard for intraoperative language mapping." This is a clinical outcome from an invasive procedure.

8. The sample size for the training set:

• The provided text does not specify a separate sample size for a training set. The clinical study described is the effectiveness study (test set). It's possible the device was developed and internally validated using other data, but those specifics are not in this document.

9. How the ground truth for the training set was established:

• As no training set details are provided in this document, the method for establishing its ground truth is not mentioned.

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The Nexstim eXimia Navigated Brain Stimulation System (NBS System) is indicated for non-invasive mapping of the primary motor cortex of the brain to its cortical gyrus. The NBS System provides information that may be used in the assessment of the primary motor cortex for pre-procedural planning. The NBS System is not intended to be used during a surgical procedure. The NBS System is intended to be used by trained clinical professionals.

Not Found

This appears to be a 510(k) clearance letter from the FDA, not a study report or clinical trial. Therefore, the provided document does not contain the information requested regarding acceptance criteria, study details, sample sizes, ground truth establishment, or expert qualifications.

The letter primarily:

• Confirms that the device, Nexstim eXimia Navigated Brain Stimulation System, has been reviewed and determined to be substantially equivalent to a legally marketed predicate device.
• Outlines general regulatory compliance requirements.
• Includes an "Indications for Use Statement" detailing what the device is approved for.

Without a separate study report or clinical trial documentation, it's impossible to answer the questions you've posed. The FDA clearance letter focuses on regulatory approval based on substantial equivalence, not on a detailed presentation of performance data from a specific study against predefined acceptance criteria.

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