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Medial longitudinal Fasciculus Pathway, Origin & Syndrome

The medial longitudinal fasciculus is basically a fine group of axons or longitudinal bundle present just a little above the midline of the brainstem or brain stem, composing of both ascending and descending batch of fibers that originates from various areas of the body. It is further associated with three different muscular connection called, oculomotor nerve, trochlear nerve, and abducens nerve.

medial longitudinal fasciculus

Medial longitudinal fasciculus Origin:

Medial longitudinal fasciculus was very first discovered by the neurologist Benedict Stilling. Later, its name was gradually changing and lastly famous Swiss anatomist Wilhelm His, Sr. called it “Medial”.

Medial longitudinal fasciculus in Spinal Cord:

The medial longitudinal fasciculus of the spinal cord relates to the area of the medial longitudinal fasciculus situated in the spinal cord. The medial longitudinal fasciculus lasts in the cervical point of the spinal cord or gray matter. A notable thing is the medial vestibulospinal path, which has the fine group of fibers that originate from the medial vestibular nucleus. The tract is a part of the anterior white column of the spinal cord. Further linkage is the ventral propriospinal tract, the anterior spinothalamic tract and lastly the lateral vestibulospinal tract of the spinal cord.

Medial longitudinal Fasciculus Pathway:

The medial longitudinal fasciculus possesses a ton of information regarding the course that the eyes usually move. It links the cranial nerve nuclei composing of the oculomotor nerve, trochlear nerve, and abducens nerve respectively, and consolidates movements targeted by the eye (frontal eye field) and give details about the head movement (from the cranial nerve, vestibulocochlear nerve). It is an essential part of saccadic eye actions along with vestibular-ocular and optokinetic reflexes.

Moreover, it includes the descending tectospinal tract and medial vestibulospinal tracts into the cervical spinal cord and innervates some muscle tissues of the neck and upper limbs.

Medial lemniscus:

The medial lemniscus, also known as Reil’s band or Reil’s ribbon, basically a significant interior part of the posterior column, that ascends from the skin via the thalamus (part of the brain). It is actually a blend bundle of heavily myelinated (a nerve posses a myelin sheath) axons that crosses each other in the brain stem, specifically in the medulla. Furthermore, it is composed of axons of nucleus gracilis and nucleus cuneatus.

Medial longitudinal fasciculus in Oculomotor Physiology:

This type of physiciology relates to the study of eye movement, via focusing up the oculomotor nerve. Now let us go in depth that actually what it is?

Innervations of the extraocular muscles:

The eyes are rotated due to the continuous motion of the six fine extraocular muscles, that gives it a push to three agonist/antagonist pairs resulting in rotations in horizontal, vertical and torsional directions.

The six extraocular muscles are controlled by three cranial nerves: the Oculomotor nerve (III), the Trochlear nerve (IV) and the Abducens nerve (VI).

The Oculomotor nerve (III) innervates the superior and inferior recti, the inferior oblique, and the medial rectus. The Trochlear nerve (IV) innervates the superior oblique. The Abducens nerve (VI) innervates the lateral rectus.

The Oculomotor and Trochlear nerves originate from the midbrain. The Abducens nerve originates from the pons.

Medial longitudinal fasciculus lesion:

It relates with the tumor or abnormally growth of the medial longitudinal fasciculus results in abnormally in blink reflexes, in easy words a person who feel this type of blinking with his/her eyes in rapid way and if it not treat in time may cause blindness forever.

Medial Longitudinal Fasciculus Syndrome:

Internuclear ophthalmoplegia is deep abnormality in conjugate lateral gaze resulting in the affected eye shows impairment of adduction. Let us elaborate.

Signs of this syndrome:

  • Medial rectus muscle weakness ipsilateral to the side of the lesion with paresis of adduction or adduction lag.
  • Abducting nystagmus of the eye contralateral to the lesion – Dissociated nystagmus.
  • Dissociated vertical nystagmus – downbeat occuring with greater torsional component rate in the contralateral eye.
  • Skew deviation – rapid production o fhypertropia on the lower side of the lesion.
  • Normal convergence.
  • Gaze evoked upright nystagmus Exacerbated top to bottom pursuit.
  • Lessened vertically vestibular capability.
  • Reducing in the amplitude saccadic intrusions that involve to the brainstem right next to the MLF.

Causes of the syndrome:

  • A weakness of adduction is as a result of reduced conduction in axons from the abducens internuclear neurons which functions to the medial rectus motor neurons in the contralateral oculomotor (nerve close to the eye) nucleus.
  • Adduction fatigue is most visible sign throughout saccades while adduction lag is forced out by signaling the patient to look towards the right and the left (i .e. producing enormous saccades).
  • The rate of the adducting eye is dependent upon a robust agonist contraction. The adducting saccade could be slow and hypometric.
  • Dissociated nystagmus could be because of: impaired capability to reduce the affected medial rectus.

Treatment of the syndrome:

This disease is mainly treated with APN technology, by passing the 2-8 Hz frequency with greater amplitude through eyes.

Features of the APN technology:

  • Amplitudes often vary , and nystagmus seems monocular.
  • Trajectories could be conjugate, but more regularly are unlike.
  • Oscillations often damp momentarily in the wake of a saccade.
  • Internuclear ophthalmoplegia commonly associated.
  • Composing of greater amplitude of electromagnetic waves.

Types Medical Longitudinal Fasciculus the syndrome:

  • Demyelinating syndrome.
  • Oculopalatal Tremor syndrome.
  • Whipple’s Disease.

Hi, This is Hamza Khan from Peshawar, Pakistan. I am a 2nd prof MBBS Student at Bannu Medical College and a hobby Blogger. The Purpose of this site is to share my knowledge and Guide new Medical Students.

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