What is PPRF lesion?
The paramedian pontine reticular formation, also known as PPRF or paraabducens nucleus, 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 horizontal gaze and saccades.
Is PPRF involved in VOR?
The pathway for the vestibulo- ocular reflex (VOR) passes through the PPRF at the level of the abducens nuclei.
What is frontal eye field lesion?
In the frontal lobe of primates, two areas play a role in visually guided eye movements: the frontal eye fields (FEF) and the medial eye fields (MEF) in dorsomedial frontal cortex. Previously, FEF lesions have revealed only mild deficits in saccadic eye movements that recovered rapidly.
What happens if the frontal eye field is damaged?
Damage to the frontal eye fields will cause deficits in voluntary eye movement to the contralateral visual field (leading to active visual search deficits), but preserved passive eye movement (as in the following of a moving object).
Is PPRF in the midbrain?
The initiation of eye movements rests to a significant degree with the frontal eye fields (FEF). For horizontal gaze, it is the paramedian pontine reticular formation (PPRF) in the mid-pons region that represents the horizontal gaze center generating conjugate horizontal movements for each eye.
Where is the lesion in one and a half syndrome?
It is clear that the eight-and-a-half syndrome lesions are located in the ipsilateral PPRF, MLF, facial nerve nucleus or nerve bundle. Or the lesions damaged ipsilateral abducens nucleus, MLF, facial nerve nucleus or nerve bundle. Therefore, the lesion is easily located in the ipsilateral pontine tegmentum.
What causes lateral gaze palsy?
Lesions of the paramedian pontine reticular formation, adjacent to the abducens nucleus, may cause lateral gaze palsy, particularly involving ipsilateral saccadic eye movements.
Where is MLF located?
The MLF are a group of fiber tracts located in the paramedian area of the midbrain and pons. They control horizontal eye movements by interconnecting oculomotor and abducens nuclei in the brain stem.
What is the frontal eye field of the brain?
The Frontal Eye Field (FEF) is a region of primate prefrontal cortex defined as the area in which low-current electrical stimulation evokes saccadic eye movements.
What stimulates frontal eye fields?
Electrical stimulation in the FEF elicits saccadic eye movements. The FEF have a topographic structure and represents saccade targets in retinotopic coordinates. The frontal eye field is reported to be activated during the initiation of eye movements, such as voluntary saccades and pursuit eye movements.
Which part of the brain controls saccades?
The parietal lobe and more particularly its posterior part, the PPC, are involved in the control of saccades and attention.
What part of the brain controls eye movement?
The cerebellum plays a pivotal role in the control of eye movements. Its core function is to optimize ocular motor performance so that images of objects of interest are promptly brought to the fovea – where visual acuity is best – and kept quietly there, so the brain has time to analyze and interpret the visual scene.
What causes medial gaze palsy?
HGPPS is caused by a mutation in the ROBO3 gene, which is important in cross-over of motor and sensory signals, preventing horizontal eye movement. In addition to the mutation, lesions in the midbrain and pons are common.
What is the Pprf?
The PPRF is the premotor structure of all ipsilateral saccades (including quick phases of nystagmus) and the generator of horizontal saccadic pulse. From: Handbook of Clinical Neurology, 2011.
What does left gaze palsy mean?
Conjugate gaze palsies are neurological disorders affecting the ability to move both eyes in the same direction. These palsies can affect gaze in a horizontal, upward, or downward direction. These entities overlap with ophthalmoparesis and ophthalmoplegia. Conjugate gaze palsy. Specialty.
What stroke causes internuclear ophthalmoplegia?
Conclusions: Isolated or predominant INO is a unique clinical stroke syndrome caused by small dorsal brainstem infarction. The pathogenesis, however, is heterogeneous, including distal occlusion of small penetrating arteries, atheromatous branch occlusion from the BA, SCA, or PCA, or major BA occlusion.
Where does the medial longitudinal fasciculus originate?
Containing both ascending and descending fiber tracts, the MLF is found on each side of the brainstem near the midline, ventral to the periaqueductal grey matter, and ascends to the interstitial nucleus (of Cajal) 1.
What do saccades indicate?
Saccades are mainly used for orienting gaze towards an object of interest. Saccades may be horizontal, vertical, or oblique. They can be both voluntarily executed at will (e.g., skimming a text) or involuntary and reflexive (e.g., during the fast phase of nystagmus or rapid eye movement sleep).