![]() |
Erstellt von Niamh McLoughlin
vor fast 7 Jahre
|
|
i) Course of tract
ii) General features of CN I Shortest cranial nerve Does not join with brainstem Has meningeal covering but is not myelinated - covered by Schwann cells iii) Primary olfactory cortex Sends nerve fibres to many areas of brain - important areas are: Piriform cortex Amygdala Olfactory tubercle Secondary olfactory cortex These areas control our memory & appreciation of smells (See CNS physiology lecture - Taste & Smell)
iv) Clinical abnormalities Anosmia Absence of sense of smell Can be temporary, permanent, progressive or congenital: Temporary = typically infection or local nasal disorders (Headcolds, flu) Permanent = head injury, tumours in olfactory groove Progressive = neurodegenerative diseases like Parkinson's or Alzheimer's Congenital = Kallmann syndrome (fail to start or finish puberty), Primary Ciliary dyskinesia (cilia don't move) Unilateral olfactory loss can be compensated for by other side - therefore patient does not tend to notice loss
i) Course of tract (See CNS anatomy Vision lecture + CNS vision physiology lec pg 4 i))
ii) General features of CN II Does not join with brainstem Surrounded by cranial meninges (See CNS vision physiology lecture for more detail)
i) Anatomical course of tract
ii) Motor & sensory functions Motor Innervates most extra-ocular muscles - move eyeball & upper eyelid Superior branch: Superior rectus - elevates eyeball Levator palpabrae superioris - raises upper eyelid Inferior branch: Inferior rectus - depresses eyeball Medial rectus - adducts eyeball Inferior oblique - elevates, abducts & laterally rotates eyeball
Sensory 2 structures - sphincter pupillae & ciliary muscles Sphincter pupillae = constriction of pupil to reduce light entering Ciliary muscles = contraction, causing lens to become 'fat & round' - short range vision Parasympathetic fibres travel in inferior branch CN III Branch into ciliary ganglion
iii) Clinical abnormalities Oculomotor nerve lesion Causes of OcNL: Increase intracranial pressure - causes nerve to be compressed against temporal bone Aneurysm posterior cerebral artery Cavernous sinus infection or trauma Diseases like diabetes, MS, Myasthenia G Clinical presentation of OcNL: Ptosis = drooping upper eyelid Due to paralysis of levator palpabrae sup. 'Down & Out' eyeball = eye rests in this position Due to paralysis recti muscles + inf. oblique Patient unable to elevate, depress or adduct eye Dilated pupil = unopposed action dilator pupillae muscle
i) Anatomical course of tract
ii) General features of CN IV Longest intracranial course of all CNs Fewest number of axons of all CNs Most fragile Only CN to emerge from posterior midbrain
iii) Motor function Innervates superior oblique muscle - depresses & intorts eye (allows us to look 'south-west' in field of vision)
iv) Clinical abnormalities Trochlear nerve palsy Vertical diplopia = 'Vertically - oriented double vision' Made worse when looking downwards & inwards Typically caused by microvascular damage due to diabetes or hypertension - also raised intracranial pressure Tested for by asking patient to follow a moving point (moved in a H-shape) with their eyes without moving their head - patient asked if any double vision occurs
i) Anatomical course of tract
ii) General features of CN V Largest cranial nerve Has 3 branches: Opthalmic nerve Maxillary nerve Mandibular nerve
iv) Divisions of CN V a) Opthalmic nerve Innervates the skin & mucous membranes of: Forehead & scalp Frontal & ethmoidal sinus Upper eyelid & its conjunctiva Cornea Dorsum of nose Involved in corneal reflex (involuntary blinking of eyelids) - stimulated by tactile, thermal or pain stimulation Opthalmic nerve detects stimulus Absent reflex suggests damage
b) Maxillary nerve Innervates skin & mucous membranes of: Lower eyelid & its conjuctiva Cheeks & maxilary sinus Nasal cavity & lateral nose Upper lip Upper front teeth & gingiva Superior palate
c) Mandibular nerve Gives sensory supply to: Mucous membranes & floor of oral cavity External ear Lower lip Chin Anterior 2/3rds tongue Lower fronal teeth & gingiva Gives motor supply to: Muscles of mastication
Useful mnemonic for remembering exit points of 3 branches! R - Foramen rotundum = Maxillary branch O - Foramen ovale = Mandibular branch S - Superior orbital fissure = Opthalmic branch
iii) Clinical relevance Would test sensory aspect using cotton bud on all 3 facial areas Test motor aspect asking patient to clench jaw & also move it left & right Test for corneal reflex
i) Anatomical course of tract
ii) General features of CN VI Has purely somatic function
iii) Motor function Innervates lateral rectus muscle Allows eyeball to abduct
iv) Clinical abnormalities Abducens nerve palsy Diplopia Medially rotated eye which cannot abduct past midline Can be caused by variety of issues (diabetic neuropathy, thrombophlebitis among others)
Möchten Sie kostenlos Ihre eigenen Notizen mit GoConqr erstellen? Mehr erfahren.