Diagnostic tests for a cervical herniated disc After the initial exam, special diagnostic imaging tests may be required to better diagnose a cervical herniated disc. MRI Scan to identify a cervical herniated disc The single best test to diagnose a herniated disc is an MRI (Magnetic Resonance Imaging) scan. An MRI scan can image any nerve root pinching caused by a herniated cervical disk. CT scan with myelogram to identify a cervical disc herniation An MRI is the best first test, although occasionally a CT scan with a myelogram may also be ordered, as it is more sensitive and can diagnose even subtle cases of nerve root pinching. Although a CT scan with myelogram is more sensitive it is also a slightly invasive test, as the myelogram dye must be injected into the spinal canal as part of the procedure. Because of the injection, a CT scan with myelogram is not usually the first test ordered. Plain CT scans (without myelogram) are for the most part not useful for the diagnosis of a herniated cervical disc. EMG to identify other conditions causing pain Occasionally, an EMG (Electromyography) may also be requested. An EMG is an electrical test that is done by stimulating specific nerves and inserting needles into various muscles in the arms or legs that may be affected from a pinched nerve. If the muscles have lost their normal innervation, there will be spontaneous electrical activity. An EMG can also help rule out other nerve entrapment syndromes that can give one arm pain, such as carpal tunnel syndrome, brachial plexitis, ulnar nerve entrapment, thoracic outlet syndrome, among other conditions.