The oculomotor nerve exits the brainstem ventrally and has two components: motor neurons that originate in the oculomotor nucleus and more peripherally situated parasympathetic fibers which arise from the Edinger-Westphal nucleus.
The Edinger-Westphal (EW) nucleus, which is part of the oculomotor nuclear complex (ONC), was first described in the literature in the 17th century.
Researchers have discovered two different cell populations within the EW nucleus.
The EW nucleus subdivides into the EW preganglionic (EWpg) population and the EW nucleus centrally projecting (EWcp) population. However, accepted nomenclature for these two groups varies.
The EWpg is what is thought of as the classic ONC—sending parasympathetic nerve fibers towards the eye. It is located in the midbrain immediately dorsal to the oculomotor nucleus near the level of the superior colliculus, which is why it is often included in the overarching term oculomotor complex.
The EWcp population of cells (the non-preganglionic EW cells), also referred to as the subgriseal paramedian midbrain neuronal stream to reflect their actual path, differ in function from the EWpg nucleus.
However, the name subgriseal paramedian midbrain neuronal stream has not found favor in the literature due to the complexity of the name and belief that the EW nucleus consisted of only one cell type. These two bodies of cells, while both referred to as the EW nucleus and intermingled from a structural standpoint in the midbrain, have fundamentally different roles in the function 1).
2: Mrzílková J, Patzelt M, Gallina P, Wurst Z, Šeremeta M, Dudák J, Krejčí F, Žemlička J, Musil V, Karch J, Rosina J, Zach P. Imaging of Mouse Brain Fixated in Ethanol in Micro-CT. Biomed Res Int. 2019 Jul 14;2019:2054262. doi: 10.1155/2019/2054262. eCollection 2019. PubMed PMID: 31392208; PubMed Central PMCID: PMC6662504.
3: Zhu N, Zhang C, Li Z, Meng Y, Feng B, Wang X, Yang M, Wan L, Ning B, Li S. Oculomotor nerve injury induces nuerogenesis in the oculomotor and Edinger-Westphal nucleus of adult dog. J Mol Neurosci. 2013 Nov;51(3):724-33. doi: 10.1007/s12031-013-0056-y. Epub 2013 Jul 7. PubMed PMID: 23832509.
4: Tanaka T, Kuchiiwa S, Izumi H. Parasympathetic mediated pupillary dilation elicited by lingual nerve stimulation in cats. Invest Ophthalmol Vis Sci. 2005 Nov;46(11):4267-74. PubMed PMID: 16249507.
5: Leimert M, Blottner D. Neuronal nitric oxide synthase (bNOS) messenger RNA and protein expression in developing rat brainstem nuclei. Neurosci Lett. 2003 May 15;342(1-2):57-60. PubMed PMID: 12727317.
6: Ichinohe N, Shoumura K. Marked miosis caused by deafferenting the oculomotor nuclear complex in the cat. Auton Neurosci. 2001 Dec 10;94(1-2):42-5. PubMed PMID: 11775706.
7: Donzelli R, Marinkovic S, Brigante L, Nikodijevic I, Maiuri F, de Divitiis O. The oculomotor nuclear complex in humans. Microanatomy and clinical significance. Surg Radiol Anat. 1998;20(1):7-12. PubMed PMID: 9574483.
8: Kaufman PL, Rohen JW, Gabelt BT, Eichhorn M, Wallow IH, Polansky JR. Parasympathetic denervation of the ciliary muscle following panretinal photocoagulation. Curr Eye Res. 1991 May;10(5):437-55. PubMed PMID: 1889229.
9: Zhuravin IA, Bures J. Extent of the tetrodotoxin induced blockade examined by pupillary paralysis elicited by intracerebral injection of the drug. Exp Brain Res. 1991;83(3):687-90. PubMed PMID: 2026211.
10: Rohen JW, Eichhorn M, Kaufman PL, Erickson-Lamy KA. Ciliary neuromuscular morphology in cynomolgus monkeys after ciliary ganglionectomy. Graefes Arch Clin Exp Ophthalmol. 1990;228(1):49-54. PubMed PMID: 2311945.
11: Erickson-Lamy KA, Kaufman PL, Polansky JR. Dissociation of cholinergic supersensitivity from receptor number in ciliary muscle. Invest Ophthalmol Vis Sci. 1988 Apr;29(4):600-5. PubMed PMID: 3356516.
12: Wathey JC. Identification of the teleost Edinger-Westphal nucleus by retrograde horseradish peroxidase labeling and by electrophysiological criteria. J Comp Physiol A. 1988 Mar;162(4):511-24. PubMed PMID: 3361460.
13: Røste GK, Dietrichs E. Cerebellar cortical and nuclear afferents from the Edinger-Westphal nucleus in the cat. Anat Embryol (Berl). 1988;178(1):59-65. PubMed PMID: 2454041.
14: Furber S, Oppenheim RW, Prevette D. Naturally-occurring neuron death in the ciliary ganglion of the chick embryo following removal of preganglionic input: evidence for the role of afferents in ganglion cell survival. J Neurosci. 1987 Jun;7(6):1816-32. PubMed PMID: 3598650; PubMed Central PMCID: PMC6568865.
15: Erickson-Lamy KA, Kaufman PL. Reinnervation of primate ciliary muscle following ciliary ganglionectomy. Invest Ophthalmol Vis Sci. 1987 Jun;28(6):927-33. Erratum in: Invest Ophthalmol Vis Sci 1987 Aug;28(8):1235. PubMed PMID: 3583631.
16: Tan J, Holstege G. Anatomical evidence that the pontine lateral tegmental field projects to lamina I of the caudal spinal trigeminal nucleus and spinal cord and to the Edinger-Westphal nucleus in the cat. Neurosci Lett. 1986 Mar 14;64(3):317-22. PubMed PMID: 3515239.
17: Hayes NL, Rustioni A. Descending projections from brainstem and sensorimotor cortex to spinal enlargements in the cat. Single and double retrograde tracer studies. Exp Brain Res. 1981;41(2):89-107. PubMed PMID: 6162664.
18: ZBROZYNA A, BONVALLET M. [INHIBITORY TONIC INFLUENCE OF THE MEDULLA OBLONGATA ON THE ACTIVITY OF THE EDINGER-WESTPHAL NUCLEUS]. Arch Ital Biol. 1963 Apr 2;101:208-22. French. PubMed PMID: 14166960.