An apparatus (2) for use in diagnosing and/or treating a neurological disorder is disclosed. The apparatus comprises a sensor device (4) designed to resemble a pen to provide a first signal containing first data representing a force applied by at least one finger of the subject, an integrated writable surface (10) to (i) provide at least one second signal containing second data representing a position of the sensor device (4) relative to the writable surface (10) and/or (ii) provide at least one third signal containing third data representing an engaging force of the sensor device on the writable surface, and a camera (20) to provide at least one fourth signal containing fourth data representing a position of at least one part of an arm of the subject holding the sensor device (4).
