Hello doctor,If a person had been diving and experienced an arterial gas embolism in the spinal cord. Specifically, it was disrupting the nerve root for the T8 or S1 dermatome. Would the whole region of the dermatome be affected with decreased sensation? Meaning, would it wrap around the torso (T8) or down the calf (S1) or is it possible to have an isolated numb spot within the T8 or S1 dermatome itself? What specifically would you do to test and map out the area of the deficiency and how would the symptoms truly present? If you were testing the cranial nerves for deficiencies, would it matter if the patient can see you touching his skin for the trigeminal nerve?
Hello. I read carefully your question and would explain that an arterial gas embolism in the spine, would not affect just a nerve territory or a dermatome. But it would lead to a much more severe condition, associated to spinal shock, inability to move the legs, inability to control the sphincter and a sensory deficit affecting both lower limbs or the four limbs and the body (in case of an upper cervical spine). A spine MRI study is necessary in such cases after a careful neurologist consult. Nevertheless, gas embolism in the spine is a really exceptional diagnosis, because it usually affects the brain. The trigeminal nerve is normal if you can feel equally the touch in both sides of the face.  For more information consult a neurologist online -->