Bilateral sixth cranial nerve palsy following lumboperitoneal shunt

Clinical presentation

Lumbar CSF drainage can reduce the volume of CSF with a drop of intracranial pressure (ICP); this commonly presents with a chronic headache and may sometimes result in a subdural collection.¹ Cranial nerve palsy following different CSF diversion procedures or dural puncture procedures (diagnostic lumbar puncture, lumbar drain, spinal/epidural block, lumbar myelography, VP shunt, and intrathecal drug delivery) is considered a rare entity as described in the literature.^2,3,4,9 Quincke was the first to describe transient sixth nerve palsy following a lumbar puncture in the early 1900s4. Li et al³ conducted a retrospective review of five cases in their institution along with a systemized literature review from the period of 1950 to 2015 for all cases diagnosed with cranial nerve palsy followed by the CSF diversion or dural puncture processes, identifying a total of 53 patients. The authors described the involvement of several cranial nerves (CNs) including CN II, CN III, CN IV, CN V, CN VI, CN VII and CN VIII. The sixth cranial nerve was most frequently involved (44 cases, 83%). Headache, particularly of the postural type, was reported as the most common warning symptom preceding the development of cranial nerve palsy, consistent with our patient’s clinical condition.^3,4 Ninety-Six percent of patients in the review achieved complete resolution after the application of a variety of treatment strategies.^3,5

Pathophysiology

The CSF drainage in the valveless LP shunt is uncontrolled and associated with intracranial hypotension.^9,10 Specifically, the abducens nerve is considered as more sensitive as compared to other cranial nerves and this shows the attribution for long intracranial course;⁹ however, anatomical studies have shown the longest intracranial course in trochlear nerve that is insensitive towards ICP based injuries.¹⁰ The increased vulnerability of the abducens nerves depends on the local anatomic factors in which the severe angulation in the point of entry at petroclival dural, which is an entrance to Dorello’s canal, is considered as the most susceptible area because there is a chance that nerves will be tethered within the canal.¹⁰ The CSF hypotension causes a high risk of traction injury at the fixation point of the nerves due to acute angulation with the descent of brainstem.¹⁰ The ischemic changes by vasospasm and vessel compression or direct mechanical stretch injury or the combination of both results in nerve palsy.^7,9

Management and outcome

Clamping of lumbar drain, hydration and bed rest following lumbar puncture, and application of an epidural blood patch are different strategies used for the management of cranial nerve palsy following CSF diversion procedures.³ Sixth cranial nerve palsy following CSF hypotension is reversible in most cases if managed early before irreversible damage occurs.¹⁰ Recently, use of programmable valve is taking the lead in prevention of complications related to CSF over drainage.¹ The correlation between risk of cranial nerve deficit and use of programmable LP valve needs further investigation. Cranial nerve palsy following LP shunt may be underreported. This case illustrates the risks associated with valveless LP shunt and underscores the importance of early intervention to prevent permanent damage.

In conclusion, the use of programmable LP shunt may be safer than valveless LP shunt and avoids the risk of CSF over-drainage and its complications.¹ Abducens and other cranial nerve palsies can also be reversible in most cases if CSF over-drainage is managed with early intervention.