In some cases, additional diagnostic testing may be performed after the physical examination and mental assessment portions of the neurological examination are complete. These additional diagnostic tests may include:

• Computed axial tomography (CAT) scan. A scanning technique that uses computer enhancement to generate three-dimensional, high-resolution images.
  
  
• Magnetic resonance imaging (MRI). Another scanning technique that uses a powerful magnetic field to produce highly refined images of the body

• Echoencephalography. Creates an ultrasound image of the brain. It is used mainly in children younger than 2 years of age because their skulls are thin enough for ultrasound waves to pass through.
  
  
• Positron emission tomography (PET) scan. Uses positron emitters (a special type of radionuclide) injected into the body to produce images of the brain’s inner structures.
  
  
• Single photon emission computed tomography (SPECT). Uses radionuclides injected into the body to produce information about blood flow and metabolic function in the brain.
  
  
• Electroencephalogram (EEG). The brain’s electrical activity is recorded and traced through a series of electrodes placed on the scalp.
  
  
• Electromyography (EMG). Small needles are inserted into a muscle to record electrical activity generated by muscles in response to nerve stimulation. This is generally performed in conjunction with a nerve conduction velocity test to identify damage to the muscles or nerves.
  
  
• Nerve conduction velocity (NCV) test. Surface electrodes are placed on the skin and minor electrical impulses are used to test the speed and strength of nerve impulses. This is generally performed in conjunction with an EMG to test for damage to the nerves and muscles.

• Biopsy. Muscle or nerve biopsies involve surgically taking a small tissue sample of an affected area of the body for laboratory analysis.
  
  
• Spinal tap. Cerebrospinal fluid is drawn with a needle from the spinal canal. This fluid is usually clear and colorless, and should not contain any blood or bacteria. Analysis of this fluid may reveal abnormalities (e.g., discoloration, presence of blood or bacteria), which may indicate a disorder.
  
  
• Cerebral angiography. Dye is injected into an artery that supplies blood flow to the brain. With the addition of imaging, it may reveal blood vessel abnormalities, such as a bulge in the artery (cerebral aneurysm), arterial inflammation (arteritis), abnormal artery configuration (arteriovenous malformation) or a blocked blood vessel (stroke).
  

  

• Doppler ultrasound scanning. Measures blood flow through the carotid arteries or through the arteries at the base of the brain. This can help reveal a patient’s risk of stroke.
  
  
• Myelography. Dye is injected and a CAT scan or x-ray image of the spine is taken.