Editing Cranial nerves (section)

===Damage===

====Compression====
Nerves may be compressed because of increased [[intracranial pressure]], a [[Mass effect (medicine)|mass effect]] of an [[intracerebral haemorrhage]], or tumour that presses against the nerves and interferes with the transmission of impulses along the nerve.<ref name=DAVIDSONS2010C>{{cite book |editor=Nicki R. Colledge |editor2=Brian R. Walker |editor3=Stuart H. Ralston |title=Davidson's principles and practice of medicine.|year=2010|publisher=Churchill Livingstone/Elsevier|location=Edinburgh|isbn=978-0-7020-3085-7|pages=787, 1215–1217|edition=21st}}</ref>  Loss of function of a cranial nerve may sometimes be the first symptom of an [[cranium|intracranial]] or [[skull base]] cancer.<ref name="Robbins">{{cite book|last=Kumar ()|first=Vinay|title=Robbins and Cotran pathologic basis of disease|year=2010|publisher=Saunders/Elsevier|location=Philadelphia, PA|isbn=978-1-4160-3121-5|page=1266|edition=8th|display-authors=etal }}</ref>

An increase in intracranial pressure may lead to impairment of the optic nerves (II) due to compression of the surrounding veins and capillaries, causing swelling of the eyeball ([[papilloedema]]).<ref>{{cite book |editor=Nicki R. Colledge |editor2=Brian R. Walker |editor3=Stuart H. Ralston |title=Davidson's principles and practice of medicine|year=2010|publisher=Churchill Livingstone/Elsevier|location=Edinburgh|isbn=978-0-7020-3085-7|page=1166|edition=21st}}</ref> A cancer, such as an [[optic nerve glioma]], may also impact the optic nerve (II). A [[pituitary tumour]] may compress the optic tracts or the [[optic chiasm]] of the optic nerve (II), leading to visual field loss. A pituitary tumour may also extend into the cavernous sinus, compressing the oculomotor nerve (III), trochlear nerve (IV) and abducens nerve (VI), leading to double-vision and [[strabismus]]. These nerves may also be affected by herniation of the [[temporal lobe]]s of the brain through the [[falx cerebri]].<ref name=DAVIDSONS2010C />

The cause of [[trigeminal neuralgia]], in which one side of the face is exquisitely painful, is thought to be compression of the nerve by an artery as the nerve emerges from the brain stem.<ref name=DAVIDSONS2010C/> An [[acoustic neuroma]], particularly at the junction between the pons and medulla, may compress the facial nerve (VII) and vestibulocochlear nerve (VIII), leading to hearing and sensory loss on the affected side.<ref name=DAVIDSONS2010C /><ref name=HARRISONS2008CN />

====Stroke====
Occlusion of blood vessels that supply the nerves or their nuclei, an [[ischemia|ischemic]] [[stroke]], may cause specific signs and symptoms relating to the damaged area. If there is a stroke of the [[midbrain]], [[pons]] or [[Medulla oblongata|medulla]], various cranial nerves may be damaged, resulting in dysfunction and symptoms of [[:Template:Lesions of spinal cord and brain|a number of different syndromes]].<ref>{{cite book|editor1=Anthony S. Fauci |editor2=T. R. Harrison |display-editors=etal|title=Harrison's principles of internal medicine|url=https://archive.org/details/harrisonsprincip00asfa |url-access=limited |year=2008|publisher=McGraw-Hill Medical|location=New York [etc.]|isbn=978-0-07-147693-5|pages=[https://archive.org/details/harrisonsprincip00asfa/page/n2564 2526]–2531|edition=17th}}</ref> [[Thrombosis]], such as a [[cavernous sinus thrombosis]], refers to a clot ([[thrombus]]) affecting the venous drainage from the [[cavernous sinus]], affects the optic (II), oculomotor (III), trochlear (IV), ophthalmic branch of the trigeminal nerve (V1) and the abducens nerve (VI).<ref name=HARRISONS2008CN>{{cite book|editor1=Anthony S. Fauci |editor2=T. R. Harrison |display-editors=etal |title=Harrison's principles of internal medicine|url=https://archive.org/details/harrisonsprincip00asfa |url-access=limited |year=2008|publisher=McGraw-Hill Medical|location=New York [etc.]|isbn=978-0-07-147693-5|pages=[https://archive.org/details/harrisonsprincip00asfa/page/n2621 2583]–2587|edition=17th}}</ref>

====Inflammation====
Inflammation of a cranial nerve can occur as a result of infection, such as viral causes like reactivated [[herpes simplex virus]], or can occur spontaneously. Inflammation of the facial nerve (VII) may result in [[Bell's palsy]].<ref name=DAVIDSONS2010>{{cite book |editor=Nicki R. Colledge |editor2=Brian R. Walker |editor3=Stuart H. Ralston |title=Davidson's principles and practice of medicine|year=2010|publisher=Churchill Livingstone/Elsevier|location=Edinburgh|isbn=978-0-7020-3085-7|pages=1164–1170, 1192–1193|edition=21st}}</ref>

[[Multiple sclerosis]], an inflammatory process resulting in a loss of the [[myelin]] sheathes which surround the cranial nerves, may cause a variety of shifting symptoms affecting multiple cranial nerves. Inflammation may also affect other cranial nerves.<ref name=DAVIDSONS2010/> Other rarer inflammatory causes affecting the function of multiple cranial nerves include [[sarcoidosis]], [[miliary tuberculosis]], and [[vasculitis|inflammation of arteries]], such as [[granulomatosis with polyangiitis]].<ref name=HARRISONS2008CN />

====Other====
Trauma to the skull, disease of bone, such as [[Paget's disease of bone|Paget's disease]], and injury to nerves during surgery are other causes of nerve damage.<ref name=HARRISONS2008CN />