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Internuclear Ophthalmoplegia
Internuclear ophthalmoplegia (INO) is a disorder of conjugate lateral gaze in which the affected eye shows impairment of adduction. When an attempt is made to gaze contralaterally (relative to the affected eye), the affected eye adducts minimally, if at all. The contralateral eye abducts, however with nystagmus. Additionally, the divergence of the eyes leads to horizontal diplopia. That is if the right eye is affected the patient will "see double" when looking to the left, seeing two images side-by-side. Convergence is generally preserved. Causes The disorder is caused by injury or dysfunction in the medial longitudinal fasciculus (MLF), a heavily myelinated tract that allows conjugate eye movement by connecting the paramedian pontine reticular formation (PPRF)-abducens nucleus complex of the contralateral side to the oculomotor nucleus of the ipsilateral side. In young patients with bilateral INO, multiple sclerosis is often the cause. In older patients with one-sided lesio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medial Longitudinal Fasciculus
The medial longitudinal fasciculus (MLF) is an area of crossed over tracts, on each side of the brainstem. These bundles of axons are situated near the midline of the brainstem. They are made up of both ascending and descending fibers that arise from a number of sources and terminate in different areas, including the superior colliculus, the vestibular nuclei, and the cerebellum. It contains the interstitial nucleus of Cajal, responsible for oculomotor control, head posture, and vertical eye movement. The medial longitudinal fasciculus is the main central connection for the oculomotor nerve, trochlear nerve, and abducens nerve. It carries information about the direction that the eyes should move. Lesions of the medial longitudinal fasciculus can cause nystagmus and diplopia, which may be associated with multiple sclerosis, a neoplasm, or a stroke. Structure The medial longitudinal fasciculus is an area of crossed over tracts, on each side of the brainstem. It is medial, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiple Sclerosis
Multiple (cerebral) sclerosis (MS), also known as encephalomyelitis disseminata or disseminated sclerosis, is the most common demyelinating disease, in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This damage disrupts the ability of parts of the nervous system to transmit signals, resulting in a range of signs and symptoms, including physical, mental, and sometimes psychiatric problems. Specific symptoms can include double vision, blindness in one eye, muscle weakness, and trouble with sensation or coordination. MS takes several forms, with new symptoms either occurring in isolated attacks (relapsing forms) or building up over time (progressive forms). In the relapsing forms of MS, between attacks, symptoms may disappear completely, although some permanent neurological problems often remain, especially as the disease advances. While the cause is unclear, the underlying mechanism is thought to be either destruction by the immune system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiple Sclerosis
Multiple (cerebral) sclerosis (MS), also known as encephalomyelitis disseminata or disseminated sclerosis, is the most common demyelinating disease, in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This damage disrupts the ability of parts of the nervous system to transmit signals, resulting in a range of signs and symptoms, including physical, mental, and sometimes psychiatric problems. Specific symptoms can include double vision, blindness in one eye, muscle weakness, and trouble with sensation or coordination. MS takes several forms, with new symptoms either occurring in isolated attacks (relapsing forms) or building up over time (progressive forms). In the relapsing forms of MS, between attacks, symptoms may disappear completely, although some permanent neurological problems often remain, especially as the disease advances. While the cause is unclear, the underlying mechanism is thought to be either destruction by the immune system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intention Tremor
Intention tremor is a dyskinetic disorder characterized by a broad, coarse, and low frequency (below 5 Hz) tremor evident during deliberate and visually-guided movement (hence the name intention tremor). An intention tremor is usually perpendicular to the direction of movement. When experiencing an intention tremor, one often overshoots or undershoots one's target, a condition known as dysmetria. Seeberger, Lauren. "Cerebellar Tremor-Definition and Treatment." The Colorado Neurological Institute Review. Fall 2005. Intention tremor is the result of dysfunction of the , particularly on the same side as the tremor in the lateral zone, which controls visually guided movements. Depending on the location of ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scanning Speech
Scanning speech is a type of ataxic dysarthria in which spoken words are broken up into separate syllables, often separated by a noticeable pause, and spoken with varying force. The sentence "Walking is good exercise", for example, might be pronounced as "Walk (pause) ing is good ex (pause) er (pause) cise". Additionally, stress may be placed on unusual syllables. The name is derived from literary scansion, because the speech pattern separates the syllables in a phrase much like scanning a poem counts the syllables in a line of poetry. There is no universal agreement about the exact definition of this term. Some sources require only a noticeable pause between syllables, while others require other speech abnormalities, such as the unusual stress pattern on syllables. Some sources consider it a common, but not necessary, feature of ataxic dysarthria; others consider it exactly synonymous with ataxic dysarthria. Cause Scanning speech, like other ataxic dysarthrias, is a sympto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
One And A Half Syndrome
The one and a half syndrome is a rare weakness in eye movement affecting both eyes, in which one cannot move laterally at all, and the other can move only in outward direction. More formally, it is characterized by "''a conjugate horizontal gaze palsy in one direction and an internuclear ophthalmoplegia in the other''". Nystagmus is also present when the eye on the opposite side of the lesion is abducted. Convergence is classically spared as cranial nerve III (oculomotor nerve) and its nucleus is spared bilaterally. Causes Causes of the one and a half syndrome include pontine haemorrhage, ischemia, tumors, infective mass lesions such as tuberculomas, demyelinating conditions like multiple sclerosis, Arteriovenous malformation, Basilar artery aneurysms and Trauma. Anatomy The syndrome usually results from single unilateral lesion of the paramedian pontine reticular formation and the ipsilateral medial longitudinal fasciculus. An alternative anatomical cause is a lesion of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medial Longitudinal Fasciculus
The medial longitudinal fasciculus (MLF) is an area of crossed over tracts, on each side of the brainstem. These bundles of axons are situated near the midline of the brainstem. They are made up of both ascending and descending fibers that arise from a number of sources and terminate in different areas, including the superior colliculus, the vestibular nuclei, and the cerebellum. It contains the interstitial nucleus of Cajal, responsible for oculomotor control, head posture, and vertical eye movement. The medial longitudinal fasciculus is the main central connection for the oculomotor nerve, trochlear nerve, and abducens nerve. It carries information about the direction that the eyes should move. Lesions of the medial longitudinal fasciculus can cause nystagmus and diplopia, which may be associated with multiple sclerosis, a neoplasm, or a stroke. Structure The medial longitudinal fasciculus is an area of crossed over tracts, on each side of the brainstem. It is medial, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PPRF
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. Input, output, and function 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 vertical saccades; the caudal PPRF may be the generator of horizontal 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 fibres to the abducens nucleus, initiating lateral eye movements. The angular velocity of the eye during horizontal s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anatomical Terms Of Location
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and anatomical axes. The meaning of terms that are used can change depending on whether an organism is bipedal or quadrupedal. Additionally, for some animals such as invertebrates, some terms may not have any meaning at all; for example, an animal that is radially symmetrical will have no anterior surface, but can still have a description that a part is close to the middle ("proximal") or further from the middle ("distal"). International organisations have determined vocabularies that are often used as standard vocabularies for subdisciplines of anatom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oculomotor Nucleus
The fibers of the oculomotor nerve arise from a nucleus in the midbrain, which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle. From this nucleus the fibers pass forward through the tegmentum, the red nucleus, and the medial part of the substantia nigra, forming a series of curves with a lateral convexity, and emerge from the oculomotor sulcus on the medial side of the cerebral peduncle. The nucleus of the oculomotor nerve does not consist of a continuous column of cells, but is broken up into a number of smaller nuclei, which are arranged in two groups, anterior and posterior. Those of the posterior group are six in number, five of which are symmetrical on the two sides of the middle line, while the sixth is centrally placed and is common to the nerves of both sides. The anterior group consists of two nuclei, an antero-medial and an antero-lateral. The nucleus of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conjugate Lateral Gaze
The term gaze is frequently used in physiology to describe coordinated motion of the eyes and neck. The lateral gaze is controlled by the paramedian pontine reticular formation (PPRF). The vertical gaze is controlled by the rostral interstitial nucleus of medial longitudinal fasciculus and the interstitial nucleus of Cajal. Conjugate gaze The ''conjugate gaze'' is the motion of both eyes in the same direction at the same time, and conjugate gaze palsy refers to an impairment of this function. The conjugate gaze is controlled by four different mechanisms: * the saccadic system that allows for voluntary direction of the gaze * the pursuit system that allows the subject to follow a moving object * nystagmus which includes both vestibular nystagmus and optokinetic nystagmus. The vestibular system restores gaze in compensation for the rotation of the head whereas the optokinetic system The optokinetic response is a combination of a slow-phase and fast-phase eye movements. It is seen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abducens Nucleus
The abducens nucleus is the originating nucleus from which the abducens nerve (VI) emerges—a cranial nerve nucleus. This nucleus is located beneath the fourth ventricle in the Anatomical terms of location, caudal portion of the pons, Anatomical terms of location, medial to the sulcus limitans. The abducens nucleus along with the internal genu of the facial nerve make up the facial colliculus, a hump at the caudal end of the medial eminence on the dorsal aspect of the pons. Structure Two primary neuron types are located in the abducens nucleus: motorneurons and interneurons. The former directly drive the contraction of the ipsilateral lateral rectus muscle via the abducens nerve (sixth cranial nerve); contraction of this muscle rotates the eye outward (abduction). The latter relay signals from the abducens nucleus to the contralateral oculomotor nucleus, where motoneurons drive the contraction of the ipsilateral medial rectus muscle (hence, contralateral to the abducens nucleus th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
