Fourth Nerve Palsy

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  • Typical acute onset of vertical diplopia without ptosis, combined with a characteristic head position
  • Head tilt and face rotation towards the healthy side with slight chin lowering
  • The affected eye is positioned higher
  • Bielschowsky head tilt test: In fourth nerve palsy, the deviation is less when the head is tilted to the opposite side; remember “BOOT = better on opposite tilt”
  • If excyclorotation is more than 7 degrees, bilateral trochlear palsy is likely

3 Step Test

  • Hypertropia due to weakness of an eye muscle: Which muscle is affected?
  • Step 1: Which eye is higher in primary position?
  • Step 2: Does hypertropia increase when looking left or right?
  • Step 3: Does hypertropia increase when tilting the head left or right?
  • Example of right trochlear palsy
  • Step 4: Double Maddox Rod Test
    • Confirmation and measurement of torsion
    • Unilateral: typically <10° excyclorotation
    • Bilateral: typically >10° excyclorotation
  • Step 5: Test in lying and sitting positions
    • For suspected skew deviation: Decrease in deviation in the lying position
      • Important, as skew deviation is almost never benign: Suspect posterior fossa lesion!
    • In trochlear palsy: no difference between lying and sitting positions

Bilateral Fourth Nerve Palsy

  • In primary position often without visible deviation
  • “Reversing” Hypertropia 1: Right eye higher when looking left, left eye higher when looking right
  • Double Maddox Rod Test with >10° excyclorotation
  • V-Phenomenon-Esotropia: Increase in squinting when looking down!
    • Therefore, automatic slight lowering of the chin
  • Bilaterally positive Bielschowsky head tilt test
  • CAUTION: Difficult to detect, always consider in trauma! Imaging required!


  • Trauma: Often bilateral
  • Vascular lesions (common in diabetes and arterial hypertension)
  • Congenital:
    • Often first symptoms (intermittent diplopia) when decompensated in adulthood
    • typically with high vertical fusion range (>10 prism diopters)
    • Look at old photos: Abnormal head posture?
  • Idiopathic
  • Demyelinating
  • Rare: Giant cell arteritis, tumor, hydrocephalus, aneurysms

Approach to isolated fourth nerve palsies

  • In patients > 50/60 years with known cardiovascular risk factors:
    • Initially, a wait-and-see approach in cases of highly probable microvascular etiology (typically not painful)
    • Exclude giant cell arteritis (clinically) -> if suspected: Blood tests (CBC, CRP, ESR)
    • Worsening of the condition is possible in the 1st – 2nd week after the event, improvement should follow thereafter
    • If the palsy worsens after 6 – 8 weeks -> Plan head MRI (with trochlear palsy, indication for imaging is more generous than with abducens palsies, as it is often not microvascular)
    • If no improvement after about 3 months -> Plan head MRI
  • In young patients < 50/60 without known cardiovascular risk factors:
    • Plan head MRI promptly (within 1 week, not urgently)
  • If fourth nerve palsy and herpes zoster ophthalmicus
    • Conduct head MRI / MRA including black blood sequences: cerebral vasculitis? (if confirmed, intravenous antiviral therapy is necessary!)
  • If fourth nerve palsies in combination with other neurological symptoms or combined cranial nerve palsies
    • Urgently refer patients to neurologists for further evaluation

Hess-Weiss-Test / (Harms) Tangent Scale

  • Simple, good test providing clues about the type of palsy
  • Possible from around the age of 6
  • Requires normal binocular vision
  • Red markings = right eye
  • Blue markings = left eye
  • 1 square on Hess-Weiss corresponds to 5 prism diopters and 5° on the tangent scale
  • Left Fourth Nerve Palsy