Myelinated Nerve Fibers

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    • By DR Rohit Gupta
      Gsvm medical college
      Co-author(s): Dr Shalini Mohan
    • Uploaded on Apr 18, 2025.
    • Last modified by Joshua Friedman on Apr 21, 2025.
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    Appears in
    Miscellaneous
    Condition/keywords
    Medullated Nerve fibres, Medulated Nerve fibre, myelinated nerve fibers, Myelinated Nerve Fibres, optic disc drusen
    Photographer
    Dr Rohit gupta
    Imaging device
    Samsung S21
    Description
    The **myelinated nerve fibers of the optic disc** (also known as **medullated nerve fibers**) are retinal nerve fibers that retain their myelin sheath as they pass through the optic nerve head. Normally, retinal nerve fibers are unmyelinated to allow for light transparency, but in some cases, myelination extends anteriorly into the retina, appearing as a striking white, feathery patch on the optic disc or peripapillary retina. ### **Key Features:** 1. **Appearance:** - Dense, white, striated patches with feathery edges. - Typically located at the superior or inferior pole of the optic disc. - May obscure retinal vessels underneath. 2. **Clinical Significance:** - Usually **benign** and asymptomatic. - **Congenital** (present at birth or early childhood). - Rarely associated with **visual field defects** (e.g., scotomas corresponding to the area of myelination). - Occasionally linked with **high myopia** or **amblyopia** if extensive. 3. **Pathophysiology:** - Failure of oligodendrocytes or Schwann cells to stop myelination at the lamina cribrosa. - Normally, myelination stops at the optic nerve head, but in this condition, it extends into the retina. 4. **Diagnosis:** - **Fundoscopy:** Classic white, feathery appearance. - **Optical Coherence Tomography (OCT):** Shows thickened retinal nerve fiber layer (RNFL). - **Visual Field Testing:** May detect defects if large. 5. **Differential Diagnosis:** - Optic disc edema - Cotton wool spots - Retinoblastoma (rarely, but must be ruled out in children) 6. **Management:** - No treatment required if asymptomatic. - Monitor for amblyopia in children. - Rare cases with significant visual impairment may need further evaluation. ### **Fun Fact:** Myelinated nerve fibers are seen in **~0.5-1%** of the population and are usually an incidental finding.

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