Horner’s syndrome is the combination of partial ptosis, myosis (small pupil), enophthalmos and hypohydrosis, and represents interruption of the ipsilateral sympathetic supply to the head anywhere along its length. There may also be associated nasal stuffiness and reduced taste sensation on the ipsilateral side (Gustav’s sign). Horner’s syndrome may occasionally occur during an otherwise unremarkable epidural block.
Palsies of cranial nerves V and VI have been reported following uncomplicated obstetric epidural anaesthesia, although much less commonly than Horner’s syndrome. In addition, cranial nerve palsies are well known to occur (albeit uncommonly) following dural puncture, and cases (including cranial nerve VII palsy) have been reported after accidental dural tap during childbirth. An idiopathic lower motor neurone lesion of cranial nerve VII (Bell’s palsy) may occur rarely in pregnancy, but there is no evidence that it is related to regional anaesthesia.
Problems and special considerations
The mechanism for Horner’s syndrome occurring during apparently normal and non- extensive epidural analgesia and anaesthesia is uncertain. Partial subdural cranial extension of local anaesthetic solution has been suggested, although there may be no other features of atypical block. The sympathetic innervation of the iris is variable and may arise from C8 to T5; in addition, sympathetic fibres are thought to be more sensitive to local anaesthetics than somatic fibres. Increased incidence in pregnancy has been suggested and may be related to the greater susceptibility of pregnant women to local anaesthetics generally or to more extensive central neural blocks in particular.
Cranial nerve palsy is also thought to be related to excessively high blockade; palsy of cranial nerve V is commonly associated with Horner’s syndrome. Cranial nerve palsy following dural puncture is thought to be related to stretching of the nerve caused by traction of intracranial contents, and it is usually associated with postdural puncture headache. Other mechanisms that have been implicated in cranial nerve paresis include raised intracranial pressure secondary to infection or thrombosis, and ischaemic neuropathy triggered by systemic hypotension.
Management options
Lesions may go unnoticed or may cause alarm to the patient, her partner or labour ward staff. In addition, if another possibly unrelated complication or event were to occur, or if general anaesthesia was administered subsequently, the pupillary signs especially may cause confusion. For cases occurring during uncomplicated epidural analgesia and anaesthesia, no specific treatment is required other than reassurance, since the signs themselves are harmless and disappear when the epidural block wears off. Once diagnosed, simple observation is all that is required, bearing in mind that the intense interest of medical and midwifery staff may cause more anxiety than the syndrome itself.
Although there are other more sinister causes of Horner’s syndrome and cranial nerve palsies, they are rare and do not usually present so acutely or for a limited duration. An association with other symptoms or signs would indicate neurological referral and/or imaging. Palsies associated with dural puncture should be managed as for the headache; it has been suggested that resolution of the palsy is less likely if epidural blood patch is delayed.
There is no evidence that the occurrence of Horner’s syndrome or cranial nerve palsy during one labour epidural predisposes the patient to the same thing during subsequent epidurals.
It must not be forgotten that some individuals naturally have unequal pupils or an asymmetrical face; it is therefore worth asking the patient and her partner whether the signs are new.
Key points
Horner’s syndrome
• Comprises partial ptosis, myosis, enophthalmos and hypohydrosis.
• May occur during an otherwise unremarkable epidural.
• Is harmless and requires no treatment if related to epidural anaesthesia.
Cranial nerve palsy
• Most commonly involves nerves V or VI, although the incidence is lower than that of Horner’s syndrome.
• Requires no treatment if of short duration and associated only with regional anaesthesia.
Further reading
Barbara R, Tome R, Barua A, et al. Transient Horner syndrome following epidural anesthesia for labor: case report and review of the literature. Obstet Gynecol Surv 2011; 66: 114-19.
Chambers DJ, Bhatia K. Cranial nerve palsy following central neuraxial block in obstetrics - a review of the literature and analysis of 43 case reports. Int J Obstet Anesth 2017; 31: 13-26.
Hofer JE, Scavone BM. Cranial nerve VI palsy after dural-arachnoid puncture. Anesth Analg 2015; 120: 644-6.