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The paramedian pontine reticular formation, or PPRF, is part of the pontine reticular formation, a brain region without clearly defined borders in the center of the pons. It is involved in the coordination of eye movements, particularly saccades.

Contents 1 Inputs, outputs, functions 2 Lesions 3 See also 4 References 5 External links

The PPRF is located anterior and lateral to the medial longitudinal fasciculus (MLF). It receives input from the superior colliculus via the predorsal bundle and from the frontal eye fields via frontopontine fibers. The rostral PPRF probably coordinates horizontal saccades; the caudal PPRF may be the generator of both horizontal and vertical saccades. In particular, activity of the excitatory burst neurons (EBNs) in the PPRF generates the "pulse" movement that initiates a saccade. In the case of horizontal saccades the "pulse" information is conveyed via axonal fibers to the abducens nucleus, initiating lateral eye movements. The angular velocity of the eye during horizontal saccade ranges from 100 to 700 degrees per second. Larger saccades have faster pulses; the PPRF is involved in this determination.^[1]

Unilateral lesions of the PPRF produce characteristic findings:^[2]

• Loss of horizontal saccades directed towards the side of the lesion, no matter the current position of gaze
• Contralateral gaze deviation (acute lesions, such as early stroke, only)
• Gaze-evoked lateral nystagmus on looking away from the side of the lesion
• Bilateral lesions produce horizontal gaze palsy and slowing of vertical saccades

• Internuclear ophthalmoplegia
• Multiple sclerosis
• One and a half syndrome
• Ophthalmoparesis
• Reticular formation
• Stroke
• Paramedian reticular nucleus

1. ↑  Brazis, P.W., Masdeu, J.C., and Biller, J. Localization in Clinical Neurology, 4th edition. Lippincott, Williams, and Wilkins, Philadelphia, 2001; pp. 213-216. ISBN 0-7817-2843-6
2. ↑  Adapted from Leigh, R.J., and Zee, D.S. The Neurology of Eye Movements, 3rd edition. Oxford University Press, Oxford, England, 1999; p. 499. ISBN 0-19-512972-5

• NeuroNames ancil-479

v • d • e Brain: rhombencephalon (hindbrain)
Myelencephalon/medulla	Arcuate nucleus of medulla, Solitary nucleus, Hypoglossal nucleus, Nucleus ambiguus, Olivary body, Inferior olivary nucleus, Cuneate nucleus, Accessory cuneate nucleus, Gracile nucleus, Inferior salivatory nucleus, Raphe nuclei (Obscurus, Magnus, Pallidus), Area postrema, Posterior nucleus of vagus nerve, Reticular formation (Gigantocellular nucleus, Parvocellular reticular nucleus, Ventral reticular nucleus, Lateral reticular nucleus, Paramedian reticular nucleus), Pyramid (Decussation)
Metencephalon/cerebellum	Vermis, Flocculus, Arbor vitae
Metencephalon/pons	Pontine tegmentum, Superior salivary nucleus, Trapezoid body, Pontine nuclei (Superior olivary nucleus, Trigeminal nerve nuclei, Abducens nucleus, Facial motor nucleus, Cochlear nuclei, Vestibular nuclei), Locus ceruleus, Paramedian pontine reticular formation, Median raphe nucleus - Reticular formation (Caudal pontine reticular nucleus, Oral pontine reticular nucleus, Tegmental pontine reticular nucleus)
Fourth ventricle	Obex, Median aperture