Light-near dissociation

Light-near dissociation (LND) is a pupillary sign that occurs when the pupillary light reaction is impaired while the near reaction (accommodative response) remains intact.

Pretectal lesions may be associated with any of 3 different patterns of pupillary deficit.

  1. Midline lesions affecting the posterior commissure cause bilateral LND,
  2. Lesions located more ventrolaterally within the periaqueductal gray cause ipsilateral LND,
  3. Lesions located more dorsolaterally within the superior brachium cause a contralateral relative afferent pupillary defect

Pretectal area

Pretectal area or pretectum, is a midbrain structure composed of seven nuclei and comprises part of the subcortical visual system

Unilateral LND

  1. Afferent conduction defect
  2. Adie pupil
    Herpes zoster ophthalmicus
  3. Aberrant regeneration of the third cranial nerve
  4. (pseudo-ARP)

Bilateral LND

  1. Neurosyphilis
  2. Type 1 diabetes mellitus
  3. Myotonic dystrophy
  4. Parinaud (dorsal midbrain) syndrome
  5. Familial amyloidosis
  6. Encephalitis
  7. Chronic alcoholism
  8. Charcot-Marie-Tooth disease
  9. Dejerine-Sottas disease

    Subscribe Medicine Question BankWhatsApp Channel

    FREE Updates, MCQs & Questions For Doctors & Medical Students

      Medicine Question Bank
      Enable Notifications OK No thanks