Ocular neuromyotonia with spastic lid closure

Ocular neuromyotonia is characterized by tonic spasms of extraocular muscles evoked by eccentric gaze that induces transient strabismus and diplopia. We report the case of a 70-year-old woman who initially presented with unilateral deficits in fifth and sixth cranial nerve functions attributed to a fifth cranial nerve schwannoma. After radiation treatment, she developed neuromyotonia and synkinesis of the ipsilateral third cranial nerve. During the attacks of neuromyotonia, the left eyelids were often spastically closed, a phenomenon not previously reported. The ocular neuromyotonia regressed spontaneously within 3 years, but components of the synkinesis persisted. Ephaptic transmission in a damaged third cranial nerve may be responsible for the neuromyotonia and synkinesis. Synkinesis is a more enduring manifestation.

[Physiological basis of a possible increase in the efficacy of the photo- and magnetotherapy of the visual nerve upon partial atrophy and ischemia]

An approach to the choice of the parameters of physiotherapeutic and biophysical influence on the visual nerve was proposed. The approach is based on parallel photo- and magnetostimulation of excitable fibers in which the morphological and electrophysiological properties of fibers and some parameters of the pathological processes associated with partial artophy and ischemia are taken into account. A method for correlating the photostimulation by light flashes (intensity 65 mWt at emission wavelength 660 nm) of a portion of the retina with the choice of the parameters of magnetic influence (amplitude 73 mT, duration of the wave front of 40 ms, and frequency of pulse sequence of about 1 Hz) on the visual nerve was developed.

Adult-onset acquired oculomotor nerve paresis with cyclic spasms: relationship to ocular neuromyotonia

PURPOSE

To describe the characteristics and significance of acquired oculomotor nerve paresis with cyclic spasm.

METHOD

Retrospective case series of two patients with a history of previous skull base irradiation for intracranial tumor who developed double vision and were found to have oculomotor nerve paresis with cyclic spasm. Both patients underwent a complete neuroophthalmologic assessment, including testing of eyelid position, pupillary size and reactivity, and ocular motility and alignment during both the paretic and spastic phases of the condition.

RESULTS

Both patients developed unilateral lid retraction and ipsilateral esotropia with limitation of abduction during the spastic phase of the cycle, with ipsilateral ptosis, exotropia, and variable limitation of adduction during the paretic phase. The cycles were continuous and were not induced or altered by eccentric gaze.

CONCLUSIONS

Cyclic oculomotor nerve paresis with spasms may occur years after irradiation of the skull base. This condition is different from the more common ocular motor disturbance that occurs in this setting-ocular neuromyotonia. However, in view of the similarity between these two disorders, it seems likely that they are caused by a similar peripheral mechanism.

Ocular neuromyotonia: three case reports with eye movement recordings

The objective of this article was to evaluate the etiologies, findings, and treatment of ocular neuromyotonia (ONM) in three case reports. The etiologies of ONM were determined by the histories, neuroradiologic tests, or biopsies. Clinical observations, videotaping, and electronic eye movement recordings documented the eye movement abnormalities. Intermittent diplopia developed several years after myelography with thorium dioxide (Thorotrast), radiation treatment for a pituitary tumor, and radiotherapy for medulloblastoma of the posterior fossa. All of the patients had intermittent, variable tropias that occurred spontaneously or were induced by eccentric gaze. One patient had a partial third nerve palsy, and another had a unilateral internuclear ophthalmoplegia (INO). ONM involved the paretic third nerve, extraocular muscles, and ipsilateral lateral rectus muscle in one patient, the paretic medial rectus muscle (INO) in one patient, a lateral rectus muscle (INO) in one patient, and a lateral rectus muscle in the last patient. Eye movement recordings were consistent with spasms of the involved muscles. Carbamazepine (Tegretol) abolished the ONM in two patients. The other patient had been taking carbamazepine for seizures and developed ONM when the dose was decreased. Increasing the dose abolished the ONM. ONM is an unusual cause of intermittent diplopia and strabismus, but its distinctive history and signs identify it easily. Damage to the peripheral cranial nerves might produce segmental demyelination, axonal hyperexcitability, and a self-perpetuating, reverberating circuit that causes spasms of the extraocular muscles.

Intermittent diplopia and strabismus caused by ocular neuromyotonia

PURPOSE

Two cases illustrate the symptoms, signs, etiologies, and treatment of ocular neuromyotonia (ONM).

METHODS

The histories, neuroradiologic tests, and/or biopsy revealed the etiologies of ONM in both patients. Clinical observations, videotaping, and electronic eye movement recordings documented the eye movements.

RESULTS

A 72-year-old man with chronic arachnoiditis following myelography with thorium dioxide (Thorotrast) developed intermittent diplopia and a partial right third nerve palsy. Left gaze induced spasm of the right medial rectus. Right gaze produced right lateral rectus spasm. A 66-year-old woman, who had radiation treatment for a pituitary tumor and acromegaly, had intermittent spasm of the left medial rectus muscle and left esotropia. The episodes occurred spontaneously and were induced by right gaze. A left internuclear ophthalmoplegia was also found. Carbamazepine (Tegretol) abolished the ONM in both patients.

CONCLUSIONS

Although ONM is an unusual cause of intermittent diplopia and strabismus, its distinctive clinical features identify it. Injury to the peripheral cranial nerves probably leads to segmental demyelination, axonal hyperexcitability, and a self-perpetuating, reverberating circuit, which causes spasms of the extraocular muscles.

Radiation sensitivity of visual and oculomotor pathways

Adverse effects of stereotactic radiosurgery on cranial nerves, especially the optic nerve and its pathways, are not yet sufficiently understood. 29 patients who underwent Gamma Knife radiosurgery for benign skull base tumors were reviewed. In all of them, parts of the visual pathways and/or other cranial nerves in the middle cranial fossa received significant doses of radiation. The dose given was correlated with neuro-ophthalmological findings during a follow-up period of 6-24 months. Cranial nerves III, IV and VI within the cavernous sinus, exposed to a dose from 4.5 to 30 Gy, did not develop signs of a neuropathy. Neither did the trigeminal nerve which received between 5 and 20 Gy. In patients with normal neuro-ophthalmological findings prior to radiosurgery, the visual pathways tolerated a dose between 7.5 to 15 Gy. However, in a group of patients with visual deficits before treatment and where the visual fibers received between 6 and 16.6 Gy, 31% deteriorated afterwards. These results indicate that the visual pathways are more at risk for radiation damage than the other cranial nerves in the region and that they may be even more vulnerable to radiation if prior to radiosurgery their function has been compromised by tumor or previous surgery.

Tolerance of cranial nerves of the cavernous sinus to radiosurgery

PURPOSE

Stereotactic radiosurgery is becoming a more accepted treatment option for benign, deep seated intracranial lesions. However, little is known about the effects of large single fractions of radiation on cranial nerves. This study was undertaken to assess the effect of radiosurgery on the cranial nerves of the cavernous sinus.

METHODS AND MATERIALS

We examined the tolerance of cranial nerves (II-VI) following radiosurgery for 62 patients (42/62 with meningiomas) treated for lesions within or near the cavernous sinus. Twenty-nine patients were treated with a modified 6 MV linear accelerator (Joint Center for Radiation Therapy) and 33 were treated with the Gamma Knife (University of Pittsburgh). Three-dimensional treatment plans were retrospectively reviewed and maximum doses were calculated for the cavernous sinus and the optic nerve and chiasm.

RESULTS

Median follow-up was 19 months (range 3-49). New cranial neuropathies developed in 12 patients from 3-41 months following radiosurgery. Four of these complications involved injury to the optic system and 8 (3/8 transient) were the result of injury to the sensory or motor nerves of the cavernous sinus. There was no clear relationship between the maximum dose to the cavernous sinus and the development of complications for cranial nerves III-VI over the dose range used (1000-4000 cGy). For the optic apparatus, there was a significantly increased incidence of complications with dose. Four of 17 patients (24%) receiving greater than 800 cGy to any part of the optic apparatus developed visual complications compared with 0/35 who received less than 800 cGy (p = 0.009).

CONCLUSION

Radiosurgery using tumor-controlling doses of up to 4000 cGy appears to be a relatively safe technique in treating lesions within or near the sensory and motor nerves (III-VI) of the cavernous sinus. The dose to the optic apparatus should be limited to under 800 cGy.

Cranial nerve damage in patients after alpha (heavy)-particle radiation to the pituitary

The records of 161 patients were reviewed to determine if radiation damage had occurred following cranial irradiation. All of these patients had received alpha-particle radiation to their pituitary glands during the period when this form of therapy was given for diabetic retinopathy. Extraocular muscle palsy developed in 11 of these patients, iridoplegia in six, and fifth nerve damage in six. All of the palsies developed within a short period following their irradiation, and a definite dose relationship was present. The dose rate was approximately 100 rads/min for all cases. Fractionation varied but it is known for all cases. The estimated doses to the third, fourth, fifth, and sixth cranial nerves was calculated at a saggital plane 13 to 15 mm from the pituitary by using computer-drawn dosimetry charts for the respective aperture size. The energetic alpha particles were produced by the 184-in synchrocyclotron at Berkeley, Calif. A dose relationship for radiation palsies was apparent.