Brain herniations are a dangerous and potentially fatal. They occur when there is a very high pressure within the skull (via mass effect from hemorrhage, trauma, or tumors) that occurs when a part of the brain is pushed/squeezed across structures within the skull. There are three main types of herniation of brain tissue. Subfalcine, uncal transtentorial, and tonsillar herniations. The subfalcine herniation is also called the cingulated herniation, this occurs when the innermost part of the frontal lobe is scraped under a portion of the falx cerebri. The uncal transtentorial herniation involves the uncus (innermost part of the temporal lobe) moving the tentorium so far that is pushes against the brainstem. A tonsillar herniation is also called a “downward cerebellar herniation,” and occurs when the cerebellar tonsils are pushed downward through the foramen magnum.

The deep fibular (also called peronal) nerve traverses the posterior side of the lower leg. The deep fibular nerve supplies tibialis anterior, extensor digitorum longus, peroneus tertius, and extensor hallucis longus. After the ankle joint, a branch of the deep fibular nerve innervates digitorum brevis and extensor hallucis brevis. 

Damage to the deep fibular nerve (often via traumatic injury to the lateral knee) results in a foot drop. Foot drop inhibits the patient to clear toes off the ground during the swing stage of walking. 

Damage to nerve roots can cause weakness, paralysis, pain, and numbness to muscles and areas innervated by the affected nerve root. When nerves of the cervical region are involved, pain is usually the first symptom to develop. Pain typically will increase gradually before other symptoms of ridiculopathy present. Due to the way nerve roots exit the vertebrae, in the cervical region the nerve root affected usually correlates to the lower vertebrae. In this case there is a narrowing of the C3/C4 space and thus the C4 nerve is affected. 

The S1 nerve is most likely to be irritated by a posteriolateral herniation of the intervertebral disc between L5 and the sacrum. To best understand this, recall that in the lumbar spine the spinal nerve exits below the associated vertebrae. Disc herniation occurs when the anulus fibrosus tears (often due to age related degeneration, lifting injuries, or trauma) and the soft nucleus pulposus is displaced and puts pressure of the nerve. Additionally the tear in the anulus fibrosus can cause the release of inflammatory mediators which will also irritate the nerve. 

Damage to nerve roots can cause weakness, paralysis, pain, and numbness to muscles and areas innervated by the affected nerve root. When nerves of the lumbar region are involved, lower back pain is usually the first symptom to develop. Pain typically will increase gradually before other symptoms of radiculopathy present. Due to the way nerve roots exit the vertebrae, in the lumbar region the nerve root affected usually correlates to the upper vertebrae. In this case there is a narrowing of the L2/L3 space and thus the L2 nerve is affected. 

Any injury to the brain can cause a release of any number of hormones into the body. Thus proper evaluation should be conducted immediately for the hormone most likely with the patients presentation. ADH is responsible for this patients abnormalities. ADH causes an increase in water re-absorption which decreases serum osmolarity and consequently, increases urine osmolarity. 

CN VII, or facial nerve, innervates the muscles responsible for facial expression. Bell's palsy is a disease that causes one side of the face to droop because the muscles are paralyzed. It can be idiopathic, associated with herpes simplex/lyme disease, or a result of CN VII being divided.