Case Reports
Successful outcome following anastomosis of a severed trochlear nerve in the middle fossa Ross Ferrier, MB BS* Vish Padmanabhan, MB BSt Andrew Hunn, MB BS, FRACSS Robin Wilkinson, DAODS
Abstract Complete return of function has been obtained following neurosurgical repair of a trochlear nerve inadvertently divided during the clipping of a basilar tip aneurysm. To date this is the second case reported in the literature. The technique of repair and the method of recording the return of function is discussed.
Key words: Cranial nerve, nerve regeneration, nerve suture, trochlear nerve. Case report A 28-year-old male presented with a subarachnoid haemorrhage which was subsequently demonstrated by angiography to have originated from an aneurysm at the bifurcation of the basilar artery. A right temporal craniotomy and subtemporal approach allowed access to the aneurysm. The infratentorial portion of the right fourth nerve was mobilised for a length of about 6 mm in order to gain access to the posterior fossa without disrupting the nerve. The aneurysm, located approximately 2 cm inferior .to the tip of the clivus, was successFrom the Royal Hobart Hospital, Hobart, Tasmania *Ophthdmolog-v Registrar tNeurosurgery Rdgistrar . 1Visiting Neurosurgeon $Senior Orthoptist
filly clipped but the right fourth nerve was accidentally divided about 4 mm proximal to its entry into the dura at some stage during the procedure. Using a 10.0 monofilament nylon suture a single t r a n s f ~ n g stitch was inserted into the nerve ends to provide anastomosis. Postoperatively the patient complained of diplopia in the primary position and especially on down gaze to the left. Initial ophthalmic review revealed abnormal head posture with tilt and turn to the left and chin depression, marked underaction of the right superior oblique and overaction of its yoke muscle, the left inferior rectus. There was also overaction of its ipsilateral antagonist, the right inferior oblique. The patient manifested right hypertropia of 6 diopters at near and 4 diopters at distance. Bielschowsky’s head tilt test was positive with increased right hypertropia on head tilt to the right. Extorsion of the right eye could be documented subjectively with the double Maddox rod and could be visualised by the change in position of the optic disc relative to the macula as documented in the other reported case.’ Recording the ocular motility pattern with a Hess chart provided clear documentation of the nature of the superior oblique palsy (Figure 1). Subsequent reviews over the next few months showed gradual and complete recovery of trochlear nerve function. Figure 2 demonstrates the improvement in finction at four months and Figure 3 demonstrates complete resolution by six months. At last attendance the patient’s only complaint was
Reprint requests: Dr RD Ferrier, C/-Ophthalmology Department, Royal Hobart Hospital, Hobart, Tasmania 7000, Australia. Successful outcome following anastomosis of a severed trochlear nerve in the middle fossa
133
f
C r c e n bclarc RigCr Ere
Figure I Hess chart demonstrating initial ocular motility pattern. Right superior oblique palsy with left inferior rectus overaction.
of mild neck discomfort due to the abnormal head posture he had previously adopted to minimise diplopia. Figure 4 demonstrates full function of the right fourth nerve.
motor nerve. End-to-end suture of the nerve ends was obtained with two 8.0 monofilament nylon sutures. Aberrant regeneration resulted but the patient was free of double vision after 19 months. T h e animal models of nerve repair demonstrated similar patterns with varying times of complete nerve regeneration. In rats with division of the fourth nerve at the anterior medullary velum, a pattern of vigorous axon growth with subsequent degeneration left variable numbers of intact neurons which interestingly grew into the ipsilateral trochlear n e r ~ e . ~ . ~
Discussion Models for the methods of repair and mechanisms of regeneration of the fourth nerve are primarily based on animal trials. Along with the case of Grimson, Ross and Tyson' the only other case of ocular motor nerve surgery was reported by Iwabuchi ei aL2and involved the repair of the oculo-
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Figure 2 Hess chart demonstrating ocular motility pattern at four months. 134
Australian and New Zealand Journal of Ophthalmology 1992; 20(2)
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Figure 3 Hess chart demonstrating ocular motility pattern at six months. Full motility
Murphy et al. found that peripheral fourth nerve section in cats resulted in an intermediate amount of cell death.5 Subsequently the somas of axotomised cells underwent a period of hypotrophy lasting about one week followed by a gradual increase in size reaching normal size at four weeks when regenerating nerves reached their target muscle. Mean axon diameters were initially smaller in the first three months increasing over the next three months and then levelling off to a diameter still slightly below normal. Despite a large range of cell death, the total number of axons remained constant at about 1000. This was achieved through an appropriate number of regenerating axonal branches per surviving cell. A maximum ratio of three to four branches per surviving cell is quoted. Studies in goldfish by Scherer and Easter demonstrated peripheral degeneration of axons and myelin sheaths after section of the fourth nerve.6 Schwann cells and macrophages contributed to the phagocytosis of the myelin sheaths. Subsequently proximal axon sprouts grew into the remaining basal lamina tube of the Schwann cell. Remyelination followed with the largest axons in the distal stump being remyelinated first. Nerve regeneration in the fourth nerve is a relatively less complicated process than with other nerves, such as the oculomotor nerve, as it is a purely motor nerve having a single target muscle. It is less prone to aberrant regeneration which complicates recovery in oculomotor nerve lesions. Also, when all injuries to the ocular motor nerves
are studied together, trochlear nerve injuries show the highest rate of recovery.' Conclusions This case history supports the proposition that intracranial suture of a divided trochlear nerve is feasible. Grimson, Ross and Tyson reported' that the repair of the trochlear nerve in their case was obtained after the trimming of the stump and epineural suture with 10.0 monofilament nylon. In our case a single 10.0 Dermalon suture transfixing and opposing the untrimmed nerve ends was used. The condition of the proximal and distal nerve ends would determine whether or not trimming is
Figure 4 Photograph of patient showing full function of the right superior oblique muscle.
Successful outcome following anastomosis of a severed trochlear nerve in the middle fossa
135
required to tidy up the surfaces to be anastomosed. Concerning the method of anastomosis, it would appear that a single transfixing suture achieves the same result as a more delicate epineural anastomosis. Methods of nerve repair appropriate to large peripheral nerves such as the funicular suture are not practical with a nerve of this size as noted by Iwabuchi et aZ.* Recent studies using fibrin glues and milliwatt COz laser welding’ may provide simpler and less traumatic methods of anastomosing this fine nerve in the future. The clinical course of this case was documented with, amongst other measurements, serial Hess charts. While Bielschowsky’s head tilt test, Maddox rod, prism cover and the observation of changes in the position of the disc with relation to the macula are important in assessing a case of this nature, the Hess charts provided quick and accurate documentation of the superior oblique palsy and subsequent recovery.
References 1. Grimson BS, Ross MJ, Tyson G. Return of function after intracranial suture of the trochlear nerve. Case Report. J Neurosurg 1984;6 1:191-2. 2. Iwabuchi T, Suzuki M, Nakaoka T, Suzuki S. Oculomotor nerve anastomosis. Neurosurgery 1982; 10:490-1. 3. Huchinson SP, McConnell P. Regeneration of nerve fibres in the anterior medullary velum of neonatal and weanling rats. Neuropathol Appl Neurobiol 1990; 16:69-83. 4. McConnell P, Berry M, Rees EL, Sievets J. The injury response of nerve fibres in the anterior medullary velum of the adult rat. Brain Res 1984;323:257-68. 5. Murphy EH, Brown J, Iannuzzelli PG, Baker R. J Comp Neurol 1990;295:685-97. 6. Scherer SS, Easter SS Jnr. J Neurocytol 1984;13:519-65. 7. Rush JA, Younge BR. Paralysis of cranial nerves 111, IV and VI. Arch Ophthalmol 1981;99:76-9. 8. Sandvos G, Cervos Navarro J, Yasargil MG. Intracranial repair of oculornotor nerve in cats. Neurochirurgia (Stuttg) 1986;29:1-8. 9. Siefert V, Stolk D. Laser assisted reconstmction of the oculomotor nerve; experimental study on the feasibility of cranial nerve repair. Neurosurgery 1989;25:579-82.
Australian and New Zealand Journal of Ophthalmology 1992; 20(2)
Successful outcome following anastomosis of a severed trochlear nerve in the middle fossa Ross Ferrier, MB BS* Vish Padmanabhan, MB BSt Andrew Hunn, MB BS, FRACSS Robin Wilkinson, DAODS
Abstract Complete return of function has been obtained following neurosurgical repair of a trochlear nerve inadvertently divided during the clipping of a basilar tip aneurysm. To date this is the second case reported in the literature. The technique of repair and the method of recording the return of function is discussed.
Key words: Cranial nerve, nerve regeneration, nerve suture, trochlear nerve. Case report A 28-year-old male presented with a subarachnoid haemorrhage which was subsequently demonstrated by angiography to have originated from an aneurysm at the bifurcation of the basilar artery. A right temporal craniotomy and subtemporal approach allowed access to the aneurysm. The infratentorial portion of the right fourth nerve was mobilised for a length of about 6 mm in order to gain access to the posterior fossa without disrupting the nerve. The aneurysm, located approximately 2 cm inferior .to the tip of the clivus, was successFrom the Royal Hobart Hospital, Hobart, Tasmania *Ophthdmolog-v Registrar tNeurosurgery Rdgistrar . 1Visiting Neurosurgeon $Senior Orthoptist
filly clipped but the right fourth nerve was accidentally divided about 4 mm proximal to its entry into the dura at some stage during the procedure. Using a 10.0 monofilament nylon suture a single t r a n s f ~ n g stitch was inserted into the nerve ends to provide anastomosis. Postoperatively the patient complained of diplopia in the primary position and especially on down gaze to the left. Initial ophthalmic review revealed abnormal head posture with tilt and turn to the left and chin depression, marked underaction of the right superior oblique and overaction of its yoke muscle, the left inferior rectus. There was also overaction of its ipsilateral antagonist, the right inferior oblique. The patient manifested right hypertropia of 6 diopters at near and 4 diopters at distance. Bielschowsky’s head tilt test was positive with increased right hypertropia on head tilt to the right. Extorsion of the right eye could be documented subjectively with the double Maddox rod and could be visualised by the change in position of the optic disc relative to the macula as documented in the other reported case.’ Recording the ocular motility pattern with a Hess chart provided clear documentation of the nature of the superior oblique palsy (Figure 1). Subsequent reviews over the next few months showed gradual and complete recovery of trochlear nerve function. Figure 2 demonstrates the improvement in finction at four months and Figure 3 demonstrates complete resolution by six months. At last attendance the patient’s only complaint was
Reprint requests: Dr RD Ferrier, C/-Ophthalmology Department, Royal Hobart Hospital, Hobart, Tasmania 7000, Australia. Successful outcome following anastomosis of a severed trochlear nerve in the middle fossa
133
f
C r c e n bclarc RigCr Ere
Figure I Hess chart demonstrating initial ocular motility pattern. Right superior oblique palsy with left inferior rectus overaction.
of mild neck discomfort due to the abnormal head posture he had previously adopted to minimise diplopia. Figure 4 demonstrates full function of the right fourth nerve.
motor nerve. End-to-end suture of the nerve ends was obtained with two 8.0 monofilament nylon sutures. Aberrant regeneration resulted but the patient was free of double vision after 19 months. T h e animal models of nerve repair demonstrated similar patterns with varying times of complete nerve regeneration. In rats with division of the fourth nerve at the anterior medullary velum, a pattern of vigorous axon growth with subsequent degeneration left variable numbers of intact neurons which interestingly grew into the ipsilateral trochlear n e r ~ e . ~ . ~
Discussion Models for the methods of repair and mechanisms of regeneration of the fourth nerve are primarily based on animal trials. Along with the case of Grimson, Ross and Tyson' the only other case of ocular motor nerve surgery was reported by Iwabuchi ei aL2and involved the repair of the oculo-
Right
Left E y e
€IF
~.
.,
Green before Lefr Eye
,I
.
--
G r e e n before R i g h t E r c
Figure 2 Hess chart demonstrating ocular motility pattern at four months. 134
Australian and New Zealand Journal of Ophthalmology 1992; 20(2)
Green before Left Ere
Grccn brlore R i i h r Eye
Figure 3 Hess chart demonstrating ocular motility pattern at six months. Full motility
Murphy et al. found that peripheral fourth nerve section in cats resulted in an intermediate amount of cell death.5 Subsequently the somas of axotomised cells underwent a period of hypotrophy lasting about one week followed by a gradual increase in size reaching normal size at four weeks when regenerating nerves reached their target muscle. Mean axon diameters were initially smaller in the first three months increasing over the next three months and then levelling off to a diameter still slightly below normal. Despite a large range of cell death, the total number of axons remained constant at about 1000. This was achieved through an appropriate number of regenerating axonal branches per surviving cell. A maximum ratio of three to four branches per surviving cell is quoted. Studies in goldfish by Scherer and Easter demonstrated peripheral degeneration of axons and myelin sheaths after section of the fourth nerve.6 Schwann cells and macrophages contributed to the phagocytosis of the myelin sheaths. Subsequently proximal axon sprouts grew into the remaining basal lamina tube of the Schwann cell. Remyelination followed with the largest axons in the distal stump being remyelinated first. Nerve regeneration in the fourth nerve is a relatively less complicated process than with other nerves, such as the oculomotor nerve, as it is a purely motor nerve having a single target muscle. It is less prone to aberrant regeneration which complicates recovery in oculomotor nerve lesions. Also, when all injuries to the ocular motor nerves
are studied together, trochlear nerve injuries show the highest rate of recovery.' Conclusions This case history supports the proposition that intracranial suture of a divided trochlear nerve is feasible. Grimson, Ross and Tyson reported' that the repair of the trochlear nerve in their case was obtained after the trimming of the stump and epineural suture with 10.0 monofilament nylon. In our case a single 10.0 Dermalon suture transfixing and opposing the untrimmed nerve ends was used. The condition of the proximal and distal nerve ends would determine whether or not trimming is
Figure 4 Photograph of patient showing full function of the right superior oblique muscle.
Successful outcome following anastomosis of a severed trochlear nerve in the middle fossa
135
required to tidy up the surfaces to be anastomosed. Concerning the method of anastomosis, it would appear that a single transfixing suture achieves the same result as a more delicate epineural anastomosis. Methods of nerve repair appropriate to large peripheral nerves such as the funicular suture are not practical with a nerve of this size as noted by Iwabuchi et aZ.* Recent studies using fibrin glues and milliwatt COz laser welding’ may provide simpler and less traumatic methods of anastomosing this fine nerve in the future. The clinical course of this case was documented with, amongst other measurements, serial Hess charts. While Bielschowsky’s head tilt test, Maddox rod, prism cover and the observation of changes in the position of the disc with relation to the macula are important in assessing a case of this nature, the Hess charts provided quick and accurate documentation of the superior oblique palsy and subsequent recovery.
References 1. Grimson BS, Ross MJ, Tyson G. Return of function after intracranial suture of the trochlear nerve. Case Report. J Neurosurg 1984;6 1:191-2. 2. Iwabuchi T, Suzuki M, Nakaoka T, Suzuki S. Oculomotor nerve anastomosis. Neurosurgery 1982; 10:490-1. 3. Huchinson SP, McConnell P. Regeneration of nerve fibres in the anterior medullary velum of neonatal and weanling rats. Neuropathol Appl Neurobiol 1990; 16:69-83. 4. McConnell P, Berry M, Rees EL, Sievets J. The injury response of nerve fibres in the anterior medullary velum of the adult rat. Brain Res 1984;323:257-68. 5. Murphy EH, Brown J, Iannuzzelli PG, Baker R. J Comp Neurol 1990;295:685-97. 6. Scherer SS, Easter SS Jnr. J Neurocytol 1984;13:519-65. 7. Rush JA, Younge BR. Paralysis of cranial nerves 111, IV and VI. Arch Ophthalmol 1981;99:76-9. 8. Sandvos G, Cervos Navarro J, Yasargil MG. Intracranial repair of oculornotor nerve in cats. Neurochirurgia (Stuttg) 1986;29:1-8. 9. Siefert V, Stolk D. Laser assisted reconstmction of the oculomotor nerve; experimental study on the feasibility of cranial nerve repair. Neurosurgery 1989;25:579-82.
Australian and New Zealand Journal of Ophthalmology 1992; 20(2)
