Musk’s medical device company, Neuralink has been denied permission to begin human trials of a revolutionary brain implant to treat intractable conditions such as paralysis and blindness by the US Food and Drug Administration (FDA). However, the death rate among apes who were forced to test the device was rather high for limited rewards and the chip has already been outclassed by less invasive technology.

The FDA listed shedloads of issues the company must sort out before human testing can begin. For example, the device uses a lithium battery which is bound to cause problems and the way the device has been designed, its wires can move to other areas of the brain where they can cause havoc. The FDA was concerned about how the device could be removed without damaging brain tissue.

A year after the rejection, Neuralink is still addressing the agency's concerns and at least three staff have said that the company cannot quickly resolve the issues. This will be news to Musk’s investors as he told them on 30 November that the company would secure FDA human-trial approval this spring.

During the hours-long November presentation, Musk said the company had submitted "most of our paperwork" to the agency, without specifying any formal application, and Neuralink officials acknowledged the FDA had asked safety questions in what they characterised as an “ongoing conversation.”

Questions have to be asked about the tech. The FDA says it has approved about two-thirds of all human-trial applications for devices on the first attempt over the past three years, which makes Neuralink unusual.

Companies that do secure human-testing approval typically conduct at least two rounds of trials before applying for FDA approval to market a device commercially.