Primary aberrant third nerve regeneration

Rate of progression and severity of neuro-ophthalmologic manifestations of cavernous sinus meningiomas

The progression of neuro-ophthalmologic signs and symptoms caused by cavernous sinus meningiomas (CSMs) was evaluated in 24 patients. Ten patients had primary involvement of the cavernous sinus by meningioma, and 14 patients had extension of a sphenoid ridge meningioma into the cavernous sinus. Eighteen patients were followed after intradural meningioma debulking. Two of these patients underwent conventional radiation therapy after surgery. The other six patients were followed without treatment. Optic neuropathy caused by extension of the CSM was the most frequently (67%) seen manifestation at the beginning of the follow-up period. Proptosis (50%), ocular motor nerve palsies (46%), and trigeminal neuropathy (33%) were also common. During a mean follow-up period of 57 months, 14 patients (58%) had no change in neurologic status, four patients (17%) had improvement in one or more parameters and six patients (25%) worsened. The patients who worsened had progression of preexisting cranial nerve palsies (two patients), developed new cranial neuropathies (three patients), or both (one patient). Patients who worsened had a significantly longer mean follow-up (76 months) than patients who remained stable or improved (47 months) (p = 0.01). Although the signs and symptoms of CSMs may worsen with time, the rate is slow and the degree is mild. These factors are important when considering treatment options.

Infranuclear ocular motor disorders

This chapter covers the very large number of possible disorders that can affect the three ocular motor nerves, the neuromuscular junction, or the extraocular muscles. Conditions affecting the nerves are discussed under two major headings: those in which the site of damage can be anatomically localized (e.g., fascicular lesions and lesions occurring in the subarachnoid space, the cavernous sinus, the superior orbital fissure, or the orbit) and those in which the site of the lesion is either nonspecific or variable (e.g., vascular lesions, tumors, "ophthalmoplegic migraine," and congenital disorders). Specific comments on the diagnosis and management of disorders of each of the three nerves follow. Ocular motor synkineses (including Duane's retraction syndrome and aberrant regeneration) and disorders resulting in paroxysms of excess activity (e.g., neuromyotonia) are then covered, followed by myasthenia gravis and other disorders that affect the neuromuscular junction. A final section discusses disorders of the extraocular muscles themselves, including thyroid disease, orbital myositis, mitochondrial disease, and the muscular dystrophies.

Paralytic strabismus: third, fourth, and sixth nerve palsy

Eye movement abnormalities constitute an important clinical sign that can be a manifestation of dysfunction of cranial nerves III, IV, and VI (the 3 ocular motor nerves). Specific motility deficits often have highly localizing value within the neuroaxis, serving to refine a differential diagnosis and guide management. This article reviews the key anatomic concepts, clinical presentation, differential diagnosis, and management of ocular motor nerve palsies. Dysfunction of an ocular motor nerve must be distinguished from other causes of abnormal eye movements, such as myasthenia gravis or thyroid eye disease, which are outside the scope of this article.

Aberrant regeneration of the oculomotor nerve: implications for neurosurgeons

✓Aberrant regeneration of cranial nerve III, otherwise known as oculomotor synkinesis, is an uncommon but well-described phenomenon most frequently resulting from trauma, tumors, and aneurysms. Its appearance usually follows an oculomotor palsy, but it can also occur primarily without any preceding nerve dysfunction. It is vital that neurosurgeons recognize this disorder because it may be the only sign of an underlying cavernous tumor or PCoA aneurysm. The tumor most often implicated is a cavernous or parasellar meningioma, but any tumor that causes compression or disruption along the course of the oculomotor nerve may cause primary or secondary misdirection. The most common clinical signs of oculomotor synkinesis consist of elevation of the upper eyelid on attempted downward gaze or adduction, adduction of the eye on attempted upward or downward gaze, and constriction of the pupil on attempted adduction. The authors present the largest series of patients with oculomotor synkinesis, including those in whom it developed after neurosurgical intervention, to illustrate various presentations. In addition, the various mechanisms that contribute to synkinesis are reviewed. Last, the treatment strategies for both oculomotor palsies and synkinesis are discussed.

Binocular diplopia. A practical approach

BACKGROUND

Diplopia is a common complaint in both inpatient and outpatient neurologic practice. Its causes are many, and special historical and examination features are important to localization and accurate diagnosis.

REVIEW SUMMARY

This review is divided into 2 sections: the first related to diagnosis and the second to treatment of binocular diplopia. In the diagnostic section, emphasis is placed on identification of historical and examination features that can help to differentiate diplopia caused by dysfunction of cranial nerves versus neuromuscular junction, or orbital extraocular muscle. Techniques available to the neurologist for examining ocular motility and ocular misalignment and focused laboratory testing to evaluate diplopia are discussed in detail. The final section covers the various treatments for binocular diplopia, with recommendations regarding the utility of each treatment for different types of diplopia.

CONCLUSIONS

A logical step-by-step approach applied to each patient with diplopia will help prevent misdiagnosis and improve patient care.

Posttraumatic abducens to oculomotor nerve misdirection

INTRODUCTION

Paradoxical patterns of extraocular muscle, eyelid, or pupillary movements can occur following injury between divisions of the oculomotor nerve, trigeminal and abducens nerves, and trigeminal and oculomotor nerves. We report three cases of unusual ocular motility and eyelid movements that are a result of aberrant connections between the abducens and oculomotor nerves.

METHODS

Three patients with unusual eye movement abnormalities after trauma were studied. A complete ophthalmic examination plus neuroradiologic evaluation were performed.

RESULTS

Each patient manifested an aberrant connection between the 6th and 3rd cranial nerves resulting in third nerve function during sixth nerve stimulation. Two patients demonstrated complete third nerve palsies except for adduction on attempted abduction. The third showed improved bilateral ptosis on abduction.

CONCLUSIONS

The neuroanatomical abnormalities involve intraorbital structures in one patient and central nervous system pathways in the others. Explanations such as retrograde regeneration, ephaptic transmission, or denervation supersensitivity do not appear to explain these unusual eye movements. The most likely mechanism involves some form of peripheral neuronal misdirection. These rare sixth to third nerve misdirection cases add support to the "neuronal misdirection hypothesis" of aberrant eye movements after trauma.

Congenital ocular aberrant innervation--new concepts

BACKGROUND

We have the impression that congenital aberrant innervations are more common than previously reported. Many varieties exist and typically involve the sixth nerve. The most common ocular miswirings are Duane's syndrome and Marcus Gunn jaw-winking ptosis. The second most common miswiring involves lateral rectus activation in upgaze causing a "Y" pattern exotropia (pseudo inferior oblique overaction). This commonly is confused with inferior oblique overaction but surgery on the obliques does not cure the condition. Lateral rectus recession and elevation are required.

METHODS

We selected demonstrative cases from our practices to illustrate a variety of congenital aberrant innervations. A literature search for previous reported cases of aberrant innervations was performed. This report is an eclectic collection of observations of individual selected cases.

RESULTS

We found aberrant innervations of unusual varieties. These miswirings involve simultaneous firing of the lateral rectus with other muscles, including: the ipsilateral superior rectus, causing "pseudo inferior oblique overaction"; the contralateral lateral rectus, causing synergistic divergence; the ipsilateral superior rectus, in upward saccades only; and the masticatory muscles, causing exotropia with sucking. The third nerve by itself rarely is involved in congenital miswirings, but commonly shows aberrant regeneration after traumatic injuries. We know of no cases of aberrant innervation involving the fourth nerve.

SUMMARY

We present cases describing these congenital aberrant innervations and discuss a unifying hypothesis as to their typical involvement of the sixth nerve.

Primary oculomotor nerve synkinesis caused by an extracavernous intradural aneurysm

Primary oculomotor nerve synkinesis is almost always caused by an intracavernous meningioma or aneurysm. We treated a patient who had signs of primary oculomotor nerve synkinesis from an unruptured extracavernous aneurysm located at the junction of the internal carotid artery and the posterior communicating artery. The aneurysm was successfully clipped, resulting in some improvement in ocular motility and alignment. Although most aneurysms affecting the subarachnoid portion of the oculomotor nerve cause an acute, painful oculomotor nerve paresis, such aneurysms may rarely produce painless primary oculomotor synkinesis and therefore should be considered in the differential diagnosis of this phenomenon.

Pseudo-Graefe's sign: a manifestation of aberrant regeneration of the fourth cranial nerve?

The phenomena involved in paradoxical upper lid retraction have been observed during recovery from paralysis of the third cranial nerve (CN). One of these phenomena is pseudo-Graefe's sign or Fuch's sign, which is characterized by elevation or retraction of the upper eyelid when the eye is looking downwards and inwards. This synkinesis is caused by an aberrant regeneration of newly formed axons of the third CN that subsequently reach muscles not originally connected with them. Pseudo-Graefe's sign may occur after congenital or acquired diseases. Acquired forms occur more frequently and result from paralysis of the third CN following various intracranial diseases: aneurysms, traumas and tumors.

Reconstruction of the third through sixth cranial nerves during cavernous sinus surgery

Sixteen reconstruction procedures of the third through sixth cranial nerves were carried out in 14 patients during operations on 149 tumors involving the cavernous sinus. A direct end-to-end anastomosis was performed in five nerves, whereas in 11 cases the nerve stumps were bridged by means of an interposing nerve graft. The sixth cranial nerve was most frequently reconstructed (nine cases). In four cases, the fifth nerve or root was repaired. The third nerve was reconstructed in two patients, and the fourth nerve was repaired in only one case. Recovery of function, either partial or complete, was observed in 13 nerves: the third in two instances, the fourth in one, the fifth in three, and the sixth in seven. No return of function occurred in three nerves. In patients with a successful recovery of cranial nerve function, either binocular function or the cosmetic result was improved. These results suggest that repair of the third through sixth cranial nerves injured during surgery should be pursued in suitable patients.

Localization of lesions of the oculomotor nerve: recent concepts

The anatomic features of the third cranial nerve (the oculomotor nerve) and the localization of lesions that affect it are reviewed. Recent considerations of the organization of the oculomotor fascicles in the ventral mesencephalon, the superior and inferior divisional palsies localized proximal to the cavernous sinus, and the possibility of the localization of ischemic oculomotor palsies to the mesencephalon rather than a peripheral site are emphasized. The characteristic manifestations of nuclear lesions (unilateral palsy of the third cranial nerve, weakness of the ipsilateral and contralateral superior rectus muscles, and bilateral incomplete ptosis) are described, as are other variations of nuclear involvement. Although proptosis is typically associated with orbital masses, it may also result from lesions of the cavernous sinus or (rarely) an intracranial lesion. Metastatic orbital tumors often are the first evidence of systemic spread in patients with cancer; infiltrative and mass lesions are the most common. Aberrant regeneration of the oculomotor nerve may occur months to years after the occurrence of an oculomotor lesion.

The cavernous sinus syndrome. An anatomical and clinical study

The cavernous sinus is often involved pathologically, which can cause ocular motor nerve palsies with or without facial sensory disturbances. Consequently several clinical features of ocular motor nerve palsies have been described. In this article we present a study of the cavernous sinus syndrome, and compare this syndrome with other nerve palsy syndromes caused by lesions in or adjacent to the cavernous sinus. The clinical features are explained by means of an anatomical study of the cavernous sinus.

Associated neurologic abnormalities in congenital third nerve palsies

A study of ten patients (six girls and four boys ranging in age from 17 months to 9 1/2 years) with congenital third nerve palsies showed that not all cases are benign without other signs of focal neurologic damage. Six of the ten children showed some degree of pupillary involvement, five had signs of oculomotor synkinesis, four had associated focal neurologic abnormalities, and two had generalized developmental delay. Only three children showed no signs of neurologic change except the third nerve palsy. Although congenital third nerve palsies are incompletely understood, these lesions probably occur as a result of the damage both to the peripheral nerve and to the brain stem itself. Signs of oculomotor synkinesis do not occur in all cases and the pupil is frequently spared.

Acquired oculomotor synkinesis

Paradoxical patterns of pupillary, lid and eye movement may follow oculomotor nerve palsy or they can develop spontaneously in patients with no known history of oculomotor palsy. The mechanism of this condition, known variously as aberrant regeneration of the third nerve, oculomotor misdirection or acquired oculomotor synkinesis, is not known, although the prevailing opinion has held that it occurs when axons regenerating within an oculomotor nerve become misdirected and innervate muscles for which they were not intended. However, there is evidence against this hypothesis. The authors critically review the various hypotheses and elucidate the controversy concerning the pathogenesis of acquired oculomotor synkinesis.

Pupil sparing in oculomotor palsy: a brief review

The clinical dictum that pupil sparing in oculomotor nerve palsy predicts an extraaxial ischemic lesion while pupil involvement predicts an extraaxial compressive lesion has some important exceptions. Two case reports and a review of the literature disclose that pupil sparing occurs in a small proportion of intraaxial and compressive subarachnoid oculomotor nerve lesions and in a large proportion of compressive cavernous sinus oculomotor nerve lesions. Careful examination is also necessary to separate examples of apparent pupil sparing in cases of aberrant regeneration and in some instances of cavernous sinus compression.

Heterotopic regeneration of peripheral nerve fibres into the subarachnoid space

Within the spinal cord meninges of SJL/J mice afflicted with chronic relapsing experimental allergic encephalomyelitis for up to seven months postinoculation, networks of aberrant regenerated nerve fibres myelinated by Schwann cells have been observed. These P.N.S. elements are believed to have been derived from incoming sensory fibres from the spinal nerve roots which had been interrupted during acute stages of the disease. This phenomenon might also have been related to the occurrence of marked nerve fibre loss and gliosis within superficial tracts in the spinal cord. P.N.S. elements within the subarachnoid space were first apparent six weeks postinoculation, and were distributed around the entire spinal cord and tended to be more concentrated around meningeal blood vessels. Schwann cells associated with these fibres frequently contained centrioles and cilia and daughter Schwann cells apparently arose from parent cells already committed to axons.