Neurology Book


Cranial Nerve 4

Aka: Cranial Nerve 4, Cranial Nerve IV, Trochlear Nerve, CN 4, Trochlear Nucleus, Cranial Nerve 4 Palsy, Trochlear Nerve Palsy, CN 4 Paralysis
  1. See Also
    1. Cranial Nerve
    2. Neuroanatomy
    3. Head and Neck Anatomy
    4. Eye Anatomy
    5. Extraocular Movement
    6. Brainstem CVA
  2. Physiology
    1. Innervates extraocular Muscle: Superior Oblique Muscle
    2. Superior Oblique Muscle passes via pulley (trochlea)
    3. Long thin nerve that is susceptible to compression (Cranial Nerve 4 and 6 are similar in this way)
      1. Paralysis (unilateral or bilateral) may occur even with generalized Increased Intracranial Pressure
      2. Contrast with the Cranial Nerve 3
        1. Thick cable-like nerve requiring significant compression for paralysis
        2. CN 3 parasympathetic fibers are susceptible to injury as they lie on the outside of CN 3
  3. Anatomy
    1. Nucleus
      1. Trochlear Nucleus is at the floor of Cerebral Aqueduct in the Midbrain
      2. Unlike all other Cranial Nerves:
        1. CN 4 crosses the midline, innervating the contralateral side (all other Cranial Nerves are ipsilateral)
        2. CN 4 exits posteriorly (all other Cranial Nerves exit anterior to the Brain Stem)
    2. Course
      1. NeuroTrochlearCN4.png
      2. Tracks around superior cerebellar, cerebral peduncles
      3. Enters tentorium cerebelli at posterior clinoid process
      4. Proceeds through lateral wall of Cavernous Sinus
      5. Enters orbit via superior orbital fissure
  4. Exam
    1. Extraocular Movement
      1. See Extraocular Movement
      2. eye_eom.png
    2. Normal function of the Superior Oblique Muscle
      1. Eye movement inferior laterally
    3. Paralysis of the Superior Oblique Muscle
      1. eye_eom.png
      2. Head Tilt toward the contralateral Shoulder
      3. Affected eye slightly elevated in primary position
      4. Can only depress affected eye slightly
  5. Causes: Cranial Nerve 4 Palsy
    1. Congenital Palsy
      1. Head position changes may occur to compensate for Strabismus and Diplopia
    2. Trauma
      1. Longest nerve course with higher risk of injury
      2. Increased Intracranial Pressure may also cause palsy (as nerve is relatively thin)
    3. MIcrovascular (small vessel disease)
      1. More common in older patients with Cardiovascular Risk Factors (e.g. Diabetes Mellitus)
  6. References
    1. Gilman (1989) Manter and Gatz Essentials of Neuroanatomy and Neurophysiology, Davis, p. 87-113
    2. Goldberg (2014) Clinical Neuroanatomy, p. 24-39
    3. Netter (1997) Atlas Human Anatomy, ICON Learning, p. 110-129

Trochlear nerve structure (C0041159)

Definition (NCI_CDISC) The cranial nerve that controls the superior oblique muscle of the eye. (NCI)
Definition (NCI) The cranial nerve that controls the superior oblique muscle of the eye.
Definition (MSH) The 4th cranial nerve. The trochlear nerve carries the motor innervation of the superior oblique muscles of the eye.
Concepts Body Part, Organ, or Organ Component (T023)
MSH D014321
SnomedCT 39322007
English Nerve, Trochlear, Nerves, Trochlear, Trochlear Nerve, Trochlear Nerves, Trochlear nerve (IV), Cranial Nerve IV, Cranial Nerve, Fourth, Cranial Nerves, Fourth, Fourth Cranial Nerve, Fourth Cranial Nerves, IV, Cranial Nerve, Nerve IV, Cranial, Nerve, Fourth Cranial, Nerves, Fourth Cranial, cranial nerve IV, pathetic nerve, Nervus trochlearis [IV], Trochlear nerve tree, Trochlear nerve [IV], superior oblique nerve, IV nerve, 4n, fourth cranial nerve, trochlear nerve, Nervus trochlearis, TROCHLEAR NERVE, Nerve IV, Nerve IVs, Fourth cranial nerve, Superior oblique nerve, Trochlear nerve, Cranial nerve IV, Trochlear nerve structure (body structure), Trochlear nerve structure, Trochlear nerve, NOS
French Nerf crânien 4, Nerf trochléaire, Quatrième nerf crânien, Nerf crânien IV, Nerf pathétique, Quatrième paire crânienne
Swedish 4:e kranialnerv
Czech nervus trochlearis, trochleární nerv, kladkový nerv, IV. hlavový nerv, IV. kraniální nerv
Finnish Telahermo
Japanese 滑車神経, 第4脳神経
German VIERTER HIRNNERV, Hirnnerv IV, IV. Hirnnerv, Nervus trochlearis
Italian Nervo cranico IV, Quarto nervo cranico, Nervo trocleare
Latvian Bloka nervs
Polish Nerw bloczkowy, Nerw IV
Norwegian Nervus trochlearis, 4. hjernenerve, Snellenerve, Hjernenerve 4
Spanish Nervio Craneal IV, IV Par Craneal, IV par craneal, cuarto nervio craneal, cuarto par craneal, cuarto par craneano, estructura del nervio patético (estructura corporal), estructura del nervio patético, nervio craneal IV, nervio oblicuo superior, nervio patético, nervio troclear, Cuarto Nervio Craneal, IV Nervio Craneal, Nervio Troclear
Portuguese IV Nervo Craniano, IV Par Craniano, Nervo Craniano IV, Nervo Troclear, Quarto Nervo Craniano
Dutch 4e hersenzenuw, IVe hersenzenuw, Nervus trochlearis
Derived from the NIH UMLS (Unified Medical Language System)

Structure of trochlear nucleus (C0152406)

Concepts Body Part, Organ, or Organ Component (T023)
MSH D013681
SnomedCT 31976003
English Nucleus of trochlear nerve, 4, nucleus of trochlear nerve, trochlear nucleus, Nucleus nervi trochlearis, Nucleus Nervi Trochleari, Trochleari, Nucleus Nervi, Trochlearis, Nucleus Nervi, Nucleus Nervi Trochlearis, Nervi Trochleari, Nucleus, Nucleus, Trochlear, Trochlear Nucleus, Nervi Trochlearis, Nucleus, Trochlear nucleus, Fourth cranial nerve nucleus, Structure of trochlear nucleus (body structure), Structure of trochlear nucleus
Spanish estructura del núcleo del nervio patético (estructura corporal), estructura del núcleo del nervio patético, núcleo del IV par craneal, núcleo del cuarto nervio craneal, núcleo del cuarto nervio craneano, núcleo del nervio patético, núcleo del nervio troclear
Derived from the NIH UMLS (Unified Medical Language System)

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