Supraorbital and supratrochlear stimulation for trigeminal autonomic cephalalgias

Trigeminal autonomic cephalalgias (TAC) is a rare primary headache disorder with challenging and limited treatment options for those unfortunate patients with severe and refractory pain. This article will review the conventional pharmacologic treatments as well as the new neuromodulation techniques designed to offer alternative and less invasive treatments. These techniques have evolved from the treatment of migraine headache, a much more common headache syndrome, and expanded towards application in patients with TAC. Specifically, the article will discuss the targeting of the supratrochlear and supraorbital nerves, both terminal branches of the trigeminal nerve.

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.

[Intraoperative identification of oculomotor, trochlear and abducent nerves in surgery of invasive cranioorbital tumors (new technique)]

BACKGROUND

Aim of the study was to evaluate effectiveness of intraoperative identification of oculomotor nerves (OMN) in resection of skull base tumors invading superior orbital fissure and cavernous sinus.

MATERIALS AND METHODS

69 patients with cranioorbital tumors operated in Burdenko Neurosurgical Institute (Moscow, Russia) since 2000 until 2005 were included in the study. They were divided into 2 groups: 19 patients treated with intraoperative identification of OMN and 50 patients in the control group. Craniorbital meningiomas were in the majority among all cases. Intraoperative identification of OMN was performed using coaxial electrode while muscular response was registered through electrodes inserted in m. levator palpebrae superioris, m. obliquus superior and m. rectus lateralis (for III, IV and VI cranial nerves, respectively). Identification of IMN trunci was repeated throughout the whole stage of tumor resection for their preservation.

RESULTS

comparison of dynamics of oculomotor dysfunction in early postoperative period in patients of both groups demonstrated that intraoperative identification of OMN allowed to decrease the frequency of oculomotor deficit. The rates in main and control groups were: for III and IV nerves--37% and 68% (p < 0.05), for VI nerve--47% and 54% (p > 0.05), respectively.

CONCLUSION

application of intraoperative identification of OMN allows to decrease the risk of oculomotor deterioration due to III and IV nerve dysfunction by 1.8 times. Technically the method is quite simple and not time-consuming procedure.

Ophthalmoplegic migraine in a 15-year-old Ethiopian: case report and literature review

The International Headache Society (IHS) defines ophthalmoplegic migraine (OM) as recurrent attacks of headache with migrainous characteristics, associated with paresis of one or more ocular cranial nerves (commonly the third cranial nerve), and in the absence of any demonstrable intracranial lesion other than MRI changes within the affected nerve. According to the IHS criteria, it is diagnosed when at least two attacks with migraine-like headaches are accompanied with, or followed within 4 days of onset by, paresis of one or more of the third, fourth or sixth cranial nerves. Parasellar, orbital fissure and posterior fossa lesions should be ruled out by appropriate investigations. It is unlikely that OM is a variant of migraine, since the headache often lasts for a week or more and there is a latent period of up to 4 days from the onset of headache to the onset of ophthalmoplegia. Furthermore, in some cases MRI shows gadolinium uptake in the cisternal part of the affected cranial nerve and this suggests that the condition may be a recurrent demyelinating neuropathy. In general, patients demonstrated a: (1) prolonged time for symptom resolution to occur (median time 3 weeks); (2) tendency for recurrent episodes to have more severe and persistent nerve involvement; (3) evidence of permanent neurological sequelae with recurrent episodes (30% of patients); (4) rapid improvement and shortened duration with corticosteroid therapy and; (5) transient, reversible MRI contrast enhancement of the affected cranial nerve (86% of patients). Different pathogenetic mechanisms, which include compressive, ischemic and inflammatory, have been suggested for OM. Here, a 15-year-old Ethiopian with recurrent attacks of headache and third nerve palsy is presented. The subsequent discussion focuses on current evidences with regard to the clinical characteristics, possible pathogenetic mechanisms and treatment. Finally, a brief discussion of the situation in Africa will be presented.

The role of intraoperative monitoring of oculomotor and trochlear nuclei -safe entry zone to tegmental lesions

OBJECTIVE

A safe entry zone to tegmental lesions was identified based on intraoperative electrophysiological findings, the compound muscle action potentials (CMAP) from the extraocular muscles, and anatomic considerations. This entry zone is bordered caudally by the intramesencephalic path of the trochlear, laterally by the spinothalamic tract, and rostrally by the caudal margin of the brachium of the superior colliculus.

METHODS

Four intrinsic midbrain lesions were operated upon via the safe entry zone using the infratentorial paramedian supracerebellar approach. All lesions involved the tegmentum and included an anaplastic astrocytoma, a metastatic brain tumor, a radiation necrosis, and a cavernous angioma. CMAP were bilaterally monitored from the inferior recti (for oculomotor function) and superior oblique (for trochlear nerve function) muscles.

RESULTS

In three of four cases, CMAP related to the oculomotor nerve were obtained upon stimulation at the cavity wall after removal of the tumor. Stimulation at the surface of the quadrigeminal plate, however, did not cause any CMAP response. Using this monitoring as an indicator, the lesions were totally removed.

CONCLUSIONS

In the surgery of tegmental lesions, CMAP monitoring from extraocular muscles is particularly helpful to prevent damage to crucial neural structures during removal of intrinsic lesions, but less so to select the site of the medullary incision. The approach via the lateral part of the colliculi is considered to be a safe route to approach the tegmental lesions.

Proposed Treatment Strategy for Cavernous Sinus Meningiomas: A Prospective Study

OBJECTIVE:

To establish a safe and effective treatment strategy for cavernous sinus (CS) meningiomas, we prospectively analyzed the outcome of a treatment protocol combining surgery and radiosurgery during the past 7 years.

METHODS:

Tumors confined to the CS and distant from the optic apparatus and the brainstem were treated with radiosurgery alone. Tumors attached to or compressing the optic apparatus and brainstem and that were larger than 3 cm in mean diameter, extended into the multiple cranial fossae, and were suspected of being malignant were treated with combined nonradical microsurgery and radiosurgery.

RESULTS:

In accordance with this treatment protocol, 40 patients aged 26 to 72 years (median, 51 yr) with primary (n = 27) or recurrent (n = 13) CS meningiomas (volume range, 0.9–39.3 cm3; median volume, 5.4 cm3) were treated with combined surgery and radiosurgery (n = 23) or radiosurgery alone (n = 17). During radiosurgery, 12 to 18 Gy (median, 16 Gy) was delivered to the tumor margin. The follow-up period ranged from 14 to 79 months (median, 47 mo). The actuarial tumor control rate was 94.1% at 5 years. The improvement of cranial nerve function was significantly frequent in patients with primary CS meningiomas (P&lt; 0.05). Permanent cranial nerve dysfunction was significantly frequent in patients with tumors compressing the brainstem or smaller than 10 cm3 (P&lt; 0.05). All 36 patients with a pretreatment Karnofsky Performance Scale score of 90 or more maintained the same range after treatment.

CONCLUSION:

Proper combination of microsurgery and radiosurgery for CS meningiomas provides excellent growth control with favorable functional state. Outcomes were better when this protocol was adopted at the initial diagnosis for patients with smaller tumors that did not compress the brainstem.

[Decompensated strabismus surso-adductorius]

Strabismus surso-adductorius is a frequent unilateral or bilateral eye movement disorder. Its clinical features include eye elevation with concomitant vertical deviation in adduction, an abnormal head posture from which the patient is unaware (head turned and tilted towards the healthy side), a moderate subjective excyclotorsion, and a positive Bielschowsky head tilt test. Despite its anglo-saxon denomination as "congenital fourth nerve palsy", it is not a paretic disorder. Strabismus surso-adductorius differs from fourth nerve palsy both by etiology and by symptoms. A proper diagnosis is important as neuroradiological examination is mandatory in cases of acquired non-traumatic fourth nerve palsy, whereas decompensated strabismus surso-adductorius can be operated on without any further investigations. Early on, the oculomotor disorder is often well compensated and it does manifest at the adult age. Asthenopia and intermittent vertical diplopia appear as the fusional mechanisms fade out. The best surgical technique for strabismus surso-adductorius is an inferior oblique weakening procedure. In severe cases a combined shortening of the superior oblique tendon may be necessary.

[Myokymia of the obliquus superior muscle and cryptogenetic epilepsy]

BACKGROUND

Myokymia of the obliquus superior muscle is a rare episodic microtremor caused by uncontrolled activities of the trochlearis nerve fibres. Epilepsy is also caused by spontaneous discharges of neurons. In our report we present an associated epilepsy which to the best of our knowledge is described for the first time.

PATIENT

An 61-year old man with twitches of the right eye for 6 weeks and a subjective feeling of eye movement was investigated at our hospital. His history was void of any ophthalmologic diseases. However, he suffered from cryptogenetic epilepsy known since childhood. The morphological and orthoptical findings of his eyes were normal. During the slit-lamp investigation a unilateral rotating microtremor of the right eye induced by looking downward was seen. The neurologic investigation, magnetic resonance imaging and assessment of the thyreoid function did not show further pathological results. The patient underwent treatment with carbamazepine. Under this therapy he did not show any symptoms of myokymia during follow-up.

SUMMARY

To the best of our knowledge this is the first case of myokymia of the obliquus superior muscle associated to epilepsy. To our opinion, any case of this syndrome should be investigated for epilepsy. A causal relation is unlikely since the most probable etiologies are either spontaneous discharges of trochlear nucleus neurons or a close contact between vessel and nerve analogously to trigeminal neuralgia.

Intra-Operative electromyographic monitoring of extra-ocular motor nerves (Nn. III, VI) in skull base surgery

BACKGROUND

Extraocular motor nerves (Nn. III, IV, VI) are at risk of damage during skull base surgery. A new recording technique was employed in 18 patients suffering from various skull base tumours in order to extend intra-operative EMG monitoring to the extra-ocular muscles.

METHODS

Selective intra-operative EMG recordings were obtained from extra-ocular muscles by placement of single-shafted bipolar needle electrodes under the guidance of B-mode ultrasound to visualise the needle tip within the target muscle in the orbital cavity.

FINDINGS

Following bipolar electrical stimulation, the oculomotor nerve (N.III) was intra-operatively identified in 5 out of 7 cases, and the abducens nerve (N.VI) in 12 out of 18 cases. Postoperative (3-6 months) oculomotor nerve function remained unchanged in 5 and improved in 2 patients. No permanent deterioration was observed. Abducens nerve function deteriorated in two patients and improved in one case, but remained unchanged in 15 cases. No side effects occurred. There was neither any distinct relation of ocular motor nerve function to the kind and extent of SMA ("spontaneous muscle activity") patterns, nor could such relationship be detected with concern to neurophysiological parameters (latencies, amplitudes) of electrically evoked CMAP ("compound muscle action potentials").

INTERPRETATION

The EMG technique proposed proved to be mainly effective as a mapping tool for intra-operative localisation and identification of ocular motor nerves in skull base surgery. However, the predictive value of conventional neurophysiological parameters for clinical outcome, seems to be rather poor. Further studies on a larger number of patients are therefore required to develop new quantification techniques which enable an intra-operative prediction of ocular motor nerve deficits. Further efforts are also necessary to extend this technique to the trochlear nerve.

Ocular motility review for 1997-1998: part I

Each year brings new scientific knowledge that builds on itself in a geometric fashion. Ocular motility basic and clinical neurosciences continue to advance with this accelerating pace. The years 1997 through 1998 brought new knowledge to the motility world. This review focuses on the clinical advances within this realm, presented in supranuclear to myopathic organization. Part II of this review will appear in the September 2000 (20:3) issue.

Isolated superior oblique palsies with electrophysiologically documented brainstem lesions

Over a 13.5-year period, we observed 10 patients with isolated superior oblique palsies in whom electrophysiological abnormalities indicated brainstem lesions. In 7 patients unilateral masseter reflex abnormalities were seen, and were located on the side of the superior oblique palsy in 2 patients and on the opposite side in 5 patients. Two patients had slowed gain of following eye movements to the side contralateral to the superior oblique palsy. Slowed adduction saccades in the eye contralateral to the superior oblique palsy were seen in 1 patient. Clinical improvement was frequently (in 7 of 10 patients) associated with improvement or normalization of electrophysiologic findings. Magnetic resonance imaging (MRI) was normal, showing no evidence of brainstem lesions in 6 patients. Unilateral superior oblique palsy may be the only clinical sign of a brainstem lesion. Although such a cause may be underdiagnosed if based on MRI-documented lesions only, it remains a rare condition.

[New view on the causes and treatment of Brown's syndrome]

The cause of the Brown's syndrome has so far been assigned to changes in the tendon sheath. Mühlendyck has proved that in Brown's syndrome patients the tendon sheath is regular whereas the symptoms are caused by changes in muscle obliquus superior or in the trochlea area. Resection of the irregular structures results in a normalisation of the active and passive elevation in adduction. 18 patients have been operated at our department according to the Mühlendyck method. Early postsurgical observations suggest positive results.

Surgically created fourth-third cranial nerve communication: temporary success in a child with bilateral third nerve hamartomas. Case report

Shortly after birth, an otherwise healthy infant developed eye deviation and ptosis due to a hamartomatous lesion of the interpeduncular segment of the right oculomotor nerve. The left nerve became similarly involved when the child was 1.5 years of age. Direct nerve repair was not possible. Instead, the trochlear nerve was divided and its proximal end was attached to the distal end of the third nerve. Elevation of the upper eyelid and partial adduction of the eye developed gradually over the ensuing 3 to 5 months. Both functions were lost after an additional 2 months, presumably as a result of tumor recurrence or neuroma formation. This case report shows that surgically created fourth-third cranial nerve communication is feasible and may merit consideration under similar circumstances.

[Unilateral paresis of the fourth cranial nerve as the only symptom of mesencephalic ischemia]

INTRODUCTION

Lesions of the fourth cranial nerves are infrequently diagnosed in cases of disorder of the oculomotor nerves. Most authors consider head injury to be the usual cause of this lesion, which is also frequently seen in association with a microvascular lesion in persons with blood flow problems.

CLINICAL CASE

We present the case of an isolated lesion of the trochlear nerve as a consequence of midbrain ischaemia.

CONCLUSIONS

Vascular disorders of the brain stem are an uncommon cause of paresis of the superior oblique muscle of the eye and exceptional as the only symptom.

[Changes in subjective cyclodeviation and objective cycloposition after modified Harada-Ito operation in acquired trochlear paralysis]

BACKGROUND

After recently published own investigations on subjective and objective cyclorotatory changes following inferior oblique recession for inferior oblique overaction, it was our aim to determine and to compare subjective and objective cyclorotatory changes following a modified Harada-Ito procedure for acquired trochlear palsy.

PATIENTS AND METHODS

Eight patients suffering from acquired uni-(n = 3) or bilateral (n = 5) trochlear palsy were investigated before surgery and 1 day, 3 days and 4 months after surgery. Subjective cyclodeviation was assessed by Harms' tangent scale. Objective cycloposition was measured by means of fundus cyclometry using an infrared Scanning Laser Ophthalmoscope.

RESULTS

The immediate postoperative incyclorotatory effect was 12 degrees in the unilateral group and 18 degrees in the bilateral group. Subjective and objective changes were nearly equal in both groups, with a subjective over-effect of 1 degree. After two days of binocular stimulation a marked regression of the surgical effect was found which still increased after four months. The long term incyclorotatory effect was subjectively and objectively nearly equal in the unilateral group which showed a relaps of subjective excyclodeviation of 5 degrees: in the bilateral group, the subjective effect was more pronounced than the objective effect, the immediate postoperative over-effect being disappeared.

CONCLUSIONS

In contrast to our results concerning inferior oblique muscle recession for strabismus sursoadductorius, subjective and objective cyclorotatory changes did not differ grossly following a modified Harada-Ito procedure. Subjective and objective short and long term regression was confirmed which objectively exceeded the amount of over-correction. As the underlying cause mechanical and sensory mechanisms are discussed.

The evaluation and treatment of extraocular motility deficits

Binocular diplopia, monocular diplopia and oscillopsia may be manifestations of skull base lesions or may result from skull base surgery. An ophthalmologic perspective on the diagnosis and treatment of these extraocular motility deficits is reviewed.

[Optic neuropathies and peripheral oculomotor disorders in patients with AIDS]

In patients with the acquired immunodeficiency syndrome (AIDS) there is an 8% incidence of neuro-ophthalmological changes. The commonest of these neuro-ophthalmological changes are: 1) Cranial nerve pareses 2) Optic neuropathy and 3) Pupil disorders. The cranial nerve pareses are usually combined, rather than single, and are due to intraparenchymatous lesions (toxoplasmosis or lymphoma) or to meningitis (tuberculous or lymphoma). The optic nerve changes tend to be papillitis due to CMV or optic neuropathy due to syphilis or to cryptococcal meningitis. Among the pupil changes, Bernard-Horner syndromes due to sympathetic involvement, Argyll-Robertson pupils due to mesencephalic tectal lesions and mydriasis associated with the common oculo-motor nerve have been described.

Transient trochlear nerve palsy following anterior temporal lobectomy for epilepsy

Three of 22 patients (14%) who underwent anterior temporal lobectomy for treatment of medically intractable epilepsy at our institution from July 1987 through July 1993 experienced diplopia immediately after surgery. We found ipsilateral paresis of the superior oblique muscle in all three patients. Their ophthalmoplegia resolved completely within 14 weeks. We did not observe any new structural or ischemic changes on postoperative MRIs to account for their deficits. Trochlear nerve palsy--not oculomotor nerve palsy, as is reported in most reference texts--is a relatively common cause of transient diplopia following temporal lobectomy. Indirect (ie, traction) injury of the trochlear nerve is a plausible mechanism that would explain this complication.

Paralytic strabismus and syndromes

In the past year, there have been interesting communications regarding third nerve palsies in children and acquired fourth nerve palsy. Several interesting articles have confirmed the benign natural history of untreated Brown's syndrome and addressed its management. Two major reviews, one on vertical diplopia and one on Duane's retraction syndrome, have provided a wealth of information and useful bibliographies.

The dynamic head-tilt test and the concept of a supranuclear trochlear palsy

The "dynamic head-tilt test" introduced in this article examines the influence of the vestibular semicircular canals on the eye muscles during the head tilt. Normally, a rotatory nystagmus results. If under certain pathological circumstances, the vestibulo-ocular reflex is transmitted only to the rectus muscles and not to the obliques, the cyclorotatory nystagmus is converted into a vertical nystagmus. We have found this condition in five cases; in two it was very pronounced. During head tilt to the right, the slow phases of the nystagmus were directed upward in the right eye and downward in the left eye. During head tilt to the left, the nystagmus directions were reversed. Since other signs of oblique muscle palsy such as incomitance and cyclotropia were lacking or inappropriately slight, the author suggests the presence of a supranuclear lesion eliminating the vestibular input to the trochlear nucleus and to the subnucleus of the inferior oblique muscle while leaving the input for voluntary and visual gaze signals intact.

Recovery of fusional convergence after systematic practice

Fusional convergence was trained systematically with orthoptic devices in three patients with a severe deficit in convergent fusion resulting from vascular (one case) or traumatic (two cases) brain damage. Within a single-subject baseline design two of the three patients showed a significant, and the third patient a moderate, recovery of fusional range. All patients showed a significant improvement in visual acuity for objects close by, improved reading performance and an increase in stereo acuity (two cases). The results suggest a considerable potential for recovery of oculomotor functions in brain-damaged patients when appropriate treatment methods are applied.

See-saw nystagmus in a patient with clinically definite MS

See-saw nystagmus (SSN) is a relatively uncommon oculomotor disorder, most often associated with parasellar or chiasmal lesions, although it has also been described in several other conditions. To date, SSN has not been reported in clinically definite multiple sclerosis (MS). We present a patient with clinically definite MS who subsequently developed SSN. Possible mechanisms of SSN are discussed. MS should be considered in the differential diagnosis of SSN.

Ocular torsion and perceived vertical in oculomotor, trochlear and abducens nerve palsies

Ocular torsion (OT) and subjective visual vertical (SVV) were determined in acute and chronic oculomotor (n = 6), trochlear (n = 21) and abducens (n = 7) palsies separately for each eye in the primary position with the head upright. Ocular torsion measured by fundus photographs was not only within normal range in all abducens palsies, but unexpectedly also in 68% of third and fourth nerve palsies which involve oblique eye muscles. Pathological OT, when measurable, was slight (2 degrees - 8 degrees), monocular and occurred either in the paretic or in the nonparetic eye. Subjective visual vertical tilts were more frequent (67% of third and fourth nerve palsies) although mostly small in amplitude (1 degree - 6 degrees). They were confined either to the paretic or the nonparetic eye depending on the duration of the palsy. Determinations of SVV were always normal under binocular viewing conditions. The dissociated occurrence of OT and SVV tilts in the paretic or the nonparetic eye was dependent on the acuteness of the palsy and reflected sensory and/or motor compensation mechanisms. Third and fourth nerve palsies cause only minor and unpredictable monocular OT and SVV tilts as distinct from the frequent binocular and conjugate tilts seen in patients with acute unilateral brainstem lesions.

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.

Intraoperative recordings of evoked extraocular muscle activities to monitor ocular motor nerve function

During 22 operations in 18 patients, we stimulated the ocular motor nerves electrically, intracranially, and recorded compound muscle action potentials (CMAP) directly from the extraocular muscles with a ring electrode that we developed. Recording electrodes were applied in 52 instances to the superior rectus, medial rectus, superior oblique, or lateral rectus muscle and to the levator palpebrae superioris in 2 instances; CMAP were recorded successfully from 22 muscles. Evoked CMAP were not recorded in 2 instances because of problems with recording equipment; in the remaining 30 instances, no evoked CMAP were recorded because 1) the oculomotor or abducens nerve was not exposed during the operation; or 2) the recording electrode on the superior oblique muscle had not been properly placed to record trochlear nerve CMAP. Placement of this electrode is difficult. Ocular motor nerve function was analyzed preoperatively and postoperatively to evaluate the usefulness of this intraoperative electrophysiological monitoring method in preventing damage to ocular motor nerves. The results of this study showed that monitoring enables surgeons to locate precisely ocular motor nerves that would otherwise have been overlooked and thus possibly injured during surgery. Monitoring results also confirmed the surgeons' visual findings, thus helping the surgeons operate with greater confidence. Further, intraoperative monitoring provided us with some insights into the pathophysiology of ocular motor nerve dysfunction caused by skull base lesions; we documented electrophysiologically the occurrence of the slowing of conduction in the ocular motor nerves. We conclude that monitoring ocular motor nerve CMAP can reduce the incidence of surgical complications such as functional blindness due to inadvertent sectioning of one of these nerves and that it would be worthwhile to conduct studies of this technique in many more cases to validate our findings.

[Length-tension measurement of oblique eye muscles in strabismus operations for differentiating trochlear paralysis and strabismus sursoadductorius]

In a group of patients with a motility typical of a superior oblique palsy (a hypertropia increasing in adduction, in down-gaze and on head-tilt, a V-pattern and an excyclotropia), we recorded length-tension diagrams of oblique eye muscles during strabismus surgery. In 14 cases a length-tension recording was made during surgery in general anaesthesia, before and after intravenous administration of succinylcholine, that produces a fierce contraction of eye muscles. Among 14 patients that had eye motilities compatible with a superior oblique muscle palsy, 7 indeed had a non-contracting superior oblique muscle, but others had oblique muscles that contracted vividly. We also made length-tension diagrams of oblique eye muscles during strabismus surgery with local, tetracain eye-drop anaesthesia. Here, the recording was made three times, while the patient looked ahead, into the field of action of the muscle and out of the field of action of the muscle. Some patients indeed had a non-contracting superior oblique muscle and a stiff inferior oblique muscle, but others had superior oblique muscles that contracted vividly, despite an eye motility typical of a superior oblique palsy, with a positive Bielschowsky head-tilt test. This finding confirms the assumption of Kaufmann, Kolling and others that these cases have a non-paretic motility disorder. Viirre et al. found in normal monkeys that disruption of fusion by one week of occlusion of one eye allowed abberrations of conjugate horizontal and vertical eye movement like upshoot-in-adduction to become manifest.(ABSTRACT TRUNCATED AT 250 WORDS)

Fourth nerve paresis and ipsilateral relative afferent pupillary defect without visual sensory disturbance. A sign of contralateral dorsal midbrain disease

We describe a patient with a left trochlear nerve paresis and a left relative afferent pupillary defect despite normal visual acuity, color vision, visual fields, and fundus examination. Magnetic resonance imaging revealed a lesion in the right dorsal midbrain extending from the brachium of the superior colliculus to the inferior colliculus. The anatomy and physiology of the pupillary light reflex are reviewed, as are possible mechanisms for the laterality of afferent pupillary defects with midbrain lesions. The presence of a trochlear nerve paresis with an ipsilateral relative afferent pupillary defect and an otherwise normal ophthalmic exam indicates a lesion in the contralateral dorsocaudal midbrain.

Pain and allodynia in postherpetic neuralgia: role of somatic and sympathetic nervous systems

The immediate effects of selective sympathetic and somatic blockades on pain and tactile allodynia in 12 patients with long-standing ophthalmic or high cervical postherpetic neuralgia were compared. For the duration of the somatic blockade, pain was completely abolished in 11 patients and allodynia in 8 patients. In contrast, during the sympathetic blockade only one patient reported total pain relief and three a marginal attenuation of pain while eight remained unchanged; and no patient reported clear alleviation of allodynia. After successful somatic blockade, pain and allodynia reappeared with tactile sensation while thermal sensation was still absent. Pain and allodynia appear to be related to sensory impulses travelling along the large rather than the small diameter fibres; and the sympathetic system may only have a limited role.

[Recordings of evoked electromyographic responses from the extraocular muscles to monitor the oculomotor, trochlear, and abducens nerve function during skull base and orbital surgery]

The methods to record evoked electromyographic responses by micro malleable clip electrodes applied directly to the extraocular muscles are described. This electrophysiological monitoring enables surgeons to localize the ocular motor nerves accurately in the skull base of the middle, posterior fossa, and orbit. In cavernous sinus surgery, electrical stimulation over the dura elicited vigorous responses from the extraocular muscles and subsequently it was possible for the surgeon to avoid severing the ocular motor nerves. In orbital surgery, distended and thinned extraocular muscles were precisely localized and preserved anatomically and functionally. These monitoring methods may play the same role as electrical stimulation to the facial nerves in acoustic neuroma surgery.

Idiopathic superior oblique palsies in children

The records of 110 patients with superior oblique palsy seen at the Boston Children's Hospital between 1966 and 1988 were reviewed. Patients with identifiable orbital or neurological disorders affecting the fourth cranial nerve or with a history of head trauma preceding their superior oblique palsy were excluded from analysis. Patients were also excluded because of prior surgery elsewhere or insufficient diagnostic information. The remaining 63 patients were considered to have idiopathic superior oblique palsies. All 63 patients presented with unilateral palsies. All had incomitant hypertropia of the affected eye, greater on gaze to the contralateral side and increased by ipsilateral head tilt. Left eyes were affected in 41 patients. The age at first ophthalmological examination was spread over the first 20 years, with heavier representation in the first 5 years and decreasing numbers in each succeeding 5-year interval. Only one patient was found to have a masked bilateral superior oblique palsy following surgery for an apparent unilateral palsy. A distinction is made between unmasking a bilateral superior oblique palsy and surgical overcorrection of a unilateral palsy. The predominant unilaterality of idiopathic superior oblique palsies is in contrast to the reported frequency of bilaterality in traumatic cases.

Hematoma of the inferior colliculus: uncommon cause of trochlear nerve deficit and contralateral sensory hemisyndrome

A 57 year old man consulted us for sudden onset of acuphenes in the right ear, followed by diplopia on forward and downward gaze and paresthesias on the right side of the body. Examination of ocular movements revealed a deficit of the superior oblique muscle of the left eye. CT and MR brainscans imaged a punctate bleed of the left inferior colliculus. The patient was discharged after 16 days still complaining of diplopia on forward and downward gaze. There was no change in neurological status at follow-up. It is rare for an intracerebral hematoma to be located in the midbrain. The case we report is distinguished by the smallness of the lesion and the uncommon neurological deficit it caused.

[Superior oblique myokymia--a case report and pathogenetic consideration]

A 30-year-old male visited us with complaints of dizziness and diplopia of abrupt onset in September, 1988. Neurological studies demonstrated paroxysmal rotatory to-and-fro oscillations of the left eye. There has been the same clinical episode at 25 years of age, lasting approximately 6 months. The characteristics of his ocular involuntary movement with the mild IVth cranial nerve paresis were as follows: quick, nonrhythmic, initially counterclockwise-rolling, more prominent in moving the left eye to the lower medial side, persisting for 1-10 seconds and rapidly repeated oscillations. When oscillations were prominent, he complained of faintness in addition to double vision. Except for the ocular signs, other neurological and laboratory examinations including cerebrospinal fluid, brain MRI and brain stem auditory evoked response, failed to disclose the precise location and nature of the lesion. Abnormal ocular movement was fluctuating for 4 months and gradually disappeared without any medication. In conclusion, the faintness could be considered to result from a lesion of reticular activating system adjacent to the IVth cranial nerve nucleus and its rostral (excitatory or inhibitory) supranuclei, and it suggests that a responsible lesion of the abnormal ocular movement is located at a region of the dorsomedial midbrain.

Brown's syndrome

Brown's syndrome is a well-recognized clinical disorder of ocular motility manifesting most notably a restriction of active and passive elevation in adduction. The original name, "superior oblique tendon sheath syndrome," is no longer appropriate, since it has been shown that the tissue surrounding the anterior superior oblique tendon is blameless as a restrictive force. "True" and "simulated" as descriptive modifiers should also be discarded, as they relate to the disproven sheath concept. Brown's syndrome occurs as a congenital or acquired, constant or intermittent condition; the common link is restriction of free movement through the trochlea pulley mechanism. The various etiologic theories are reviewed and the spectrum of medical and surgical treatments are described and evaluated. Evidence suggests that subtypes of Brown's syndrome lie on a single continuum and that spontaneous resolution occurs in each group, probably more often than previously recognized. A simplified classification scheme is encouraged and possible future directions in Brown's syndrome research are introduced.

Familial recurrent cranial nerve palsies

Family cases of recurrent cranial nerve palsies are seldom reported. This paper presents a family with recurrent facial and ocular nerve palsies in 2 brothers. Their father and his sister had Bell's palsies. Examinations provided no explanation. Six previous reports of families with recurrent cranial nerve palsies are summarized. The pedigrees speak in favour of an autosomal dominant mode of inheritance of predisposing factors. The pathogenetic mechanism might be vascular or autoimmune, but is still unknown.

Measurement of vertical deviations in different gaze positions in patients with a superior oblique palsy

Objective measurements in eight consecutive patients with an isolated congenital superior oblique palsy using a head tilt technique, with gaze directed toward a fixed distance target, and a second technique with gaze directed at a movable near object in different fields of gaze each identified the same oblique position of maximal vertical deviation. We call the latter technique "field-directed." In distinction to the controversy that exists as to which method correctly diagnoses an isolated superior oblique palsy, either technique can be used to direct the surgical correction of this palsy. Superimposing a head tilt on the field-directed technique affected measurements in 16 of the 20 instances where tested. Despite the necessity of avoiding an inadvertent head tilt the field-directed technique is considerably easier to perform and more comfortable for the patient to endure in determining the position of maximal vertical deviation.

Trochlear nerve pareses with brainstem lesions

Three cases of radiographic localization of fourth nerve lesions are reported: case 1--bilateral pareses due to traumatic contusion; case 2--left paresis from a collicular gunshot wound; and case 3--bilateral pareses due to a (cysticercal) cyst in the caudal cerebral aqueduct.

[Fisher's one-and-one half syndrome. Involvement of the 6th cranial nerve nucleus and association with paralytic pontine exotropia]

Total lateral paralysis in a case of "One and half" Fisher's syndrome accompanied by paralytic pontine exotropia is described. Oculographic investigation indicates involvement of the nucleus of the VIth cranial nerve. Paralytic pontine exotropia, may therefore be encountered where the VIth nucleus is involved.

The injury response of nerve fibres in the anterior medullary velum of the adult rat

The injury response of myelinated central nervous system (CNS) axons was documented in the anterior medullary velum (AMV) of the adult rat. Study of silver-stained AMV whole-mounts revealed sprouting of injured axons as early as 14 h post-lesion (hpl), with a complex network of fibres formed by 48 hpl. Signs of fibre degeneration were also apparent from 48 hpl, increasing in extent until 15 days post-lesion (dpl). Fragmentation was largely confined to specific fibre bundles, constituted by the distal portions of severed axons. Although some degeneration of regenerated axons was evident from 15-20 dpl, many remained intact beyond this time, particularly in the area adjacent to the exit of the trochlear nerve, where most regenerated fibres penetrated the ipsilateral trochlear nerve. Counts of HRP filled neurons in the trochlear nucleus after injection of the superior oblique muscle showed that axons entering the IVth nerve rootlet were exclusively ipsilateral trochlear fibres. Less than 50% regenerated; most other severed axons degenerated. The few axons remaining in the AMV may have been fibres, undamaged by the original lesion, which normally course longitudinally through the ipsilateral AMV. These results show that IVth nerve fibres preferentially enter IVth nerve rootlets and, in so doing, survive the effects of injury. Most other CNS axons in the AMV which do not enter the trochlear root probably degenerate.