Alteration of orbicularis oculi reflex by posterior fossa tumors

Analysis of the corneal reflex with air puff: normal controls and patient groups

Though there are several reports published about the corneal reflex elicited by different methods, a standardized electrophysiologic study with air puff in man has not been published. The aim of this study is to standardize the corneal reflex elicited by air puff to cornea. The authors studied the corneal reflex with air puff and direct touch by using a standardized method in patients with thalamic hemorrhage (n = 15), hemispheric infarction (n = 9), brainstem infarction (n = 9), multiple sclerosis (n = 12), and Bell's palsy (n = 12) and in normal control subjects (n = 21). The conventional blink reflex (BR) was also studied. The reflex responses were recorded from both orbicularis oculi muscles by air puff and direct touch to cornea in addition to the electrical stimulation of the supraorbital nerve. No statistical difference could be detected between the responses elicited by air puff or direct touch to cornea (P > 0.05). Corneal reflex responses were statistically different from the R2 response of the BR (P < 0.005). Because the responses elicited by direct touch and air puff to cornea are identical, air puff to cornea can be used confidently to study the corneal reflex.

Value of blink reflex in assessing V and VII nerve function in patients with C. P. Angle tumours- a prospective study of 75 patients

This propsective study analyses the role of blink reflex (BR) in 75 patients with Cerebellopontine Angle (CPA) tumours. The aim was to find out the subclinical involvement from the blink reflex findings. Fifth nerve was clinically involved in 82.7% patients while, BR was able to detect afferent abnormality only in 54% patients. The seventh nerve was clinically involved in 74.7% and blink reflex could detect the efferent abnormality is 72% patients. Thus, clinicoelectrophysiological correlation was 56.4% and 72% for V and VII nerve respectively. In the patients in whom there was no V or VII nerve involvement BR showed VII nerve involvement in 12% patients. The subclinical involvement of the V nerve and the brainstem were detected by BR in 4% patients each. In conclusion BR is good test for the assessment of VII nerve function as compared to V nerve function. BR could pick of subclinical involvement in 20% patients.

The blink reflex before and after percutaneous glycerol rhizotomy in patients with trigeminal neuralgia--a prospective study of 28 patients

The blink reflex was prospectively studied in 28 patients with trigeminal neuralgia, prior-to and following percutaneous glycerol rhizotomy to the Gasserian ganglion. Fifteen patients (54%) had varying degrees of sensory loss in the trigeminal nerve distribution already before glycerol injection. Three more patients developed sensory loss following glycerol injection. Thus following glycerol injection 18 patients had graded sensory loss. Pre-injection the blink reflex showed abnormal R1 wave in 57% patients, while direct and consensual R2 waves were abnormal in 43% and 48%, respectively. Post-injection R1 wave was abnormal in 64% patients. Direct R2 waves were abnormal in 33% patients. Thus clinical findings of sensory loss correlated well with pre-and post-injection blink reflex abnormality. Postoperatively R1 and ipsilateral R2 latencies from the side of the injection deteriorated and consensual R2 latency improved, thus, signifying better function on the contralateral side following relief of pain by glycerol rhizotomy.

Cranial nerve conduction and needle electromyography in patients with acoustic neuromas: a model of compression neuropathy

Of 45 patients with acoustic neuromas (0.3-5.0 cm), 73% had facial nerve impairment on electrophysiologic testing, but only 16% had facial weakness. Cranial nerve conduction was the most sensitive measurement, especially prolongation of the ipsilateral R1 latency of the blink reflex compared with that of the contralateral reflex. The severity of nerve conduction abnormality was highly correlated with tumor size. Our results confirm and quantitate the sensitivity of nerve action potential latency in response to chronic nerve compression.

Lesch-Nyhan syndrome with delayed onset of self-mutilation: hyperactivity of interneurons at the brainstem and blink reflex

We studied a case of Lesch-Nyhan syndrome with delayed onset of self-mutilation. Athetotic cerebral palsy and mental retardation were diagnosed at 1 year old, but the disease was not suspected until age 8 years when he began biting his lips and fingers. There was no obvious alteration of catecholamine in urine and CSF. We attempted to induce a series of blink reflexes by electric, mechanical and photic procedures. The R1 amplitude increased and the latency of the R2 shortened compared with controls. This shows that not only orbicularis motoneuron itself, but also uncrossed interneurons, are in a state of hyperexcitability. The contralateral R2 was poor which was in favour of hypoexcitability of the crossed interneurons at the brainstem. The significant large response was obtained by photic procedure which was in favour of hyperexcitability of the motoneurons. Therefore, it is demonstrated that a thorough examination of blink reflexes provides a useful method for examination of a state of the underlying neural activity.

Effects of general anesthesia on the human blink reflex

The blink reflex was studied in 10 patients undergoing elective procedures under general anesthesia. Anesthetic agents were isoflurane, halothane, nitrous oxide, methohexital, and thiopental in various combinations. At induction, blink reflexes were diminished by low-dose thiopental (1-1.5 mg/kg) and abolished by high-dose thiopental (4-8 mg/kg) and methohexital (1.5 mg/kg). Blink reflexes were absent during halogenated volitile inhalational anesthesia and did not return until patients were in the recovery room, well after end-tidal anesthetic levels were zero by mass spectroscopy. Recovery of consciousness and the ability to blink on command often preceded return of any blink reflex activity, indicating that the blink reflex is not useful as a postoperative test of facial nerve function in the operating room after anesthesia. In six patients, blink reflexes were still diminished 2-3 hours after cessation of anesthesia, at a time when patients were fully oriented and corneal and eyelid reflexes were clinically normal. This finding suggests that the blink reflex might be a sensitive test of subtle CNS dysfunction after inhalational anesthesia and potentially could serve as a useful objective indicator of recovery from anesthesia for outpatient surgery.

A comparative study of brain-stem auditory evoked potentials and blink reflexes in posterior fossa tumor patients

Brain-stem auditory evoked potentials (BAEP's) and blink reflexes (BR's) were recorded from 40 patients with clinical and radiological evidence of posterior fossa tumors. They were examined in three groups according to the anatomical location of the lesion: Group A included 15 patients with midline tumors; Group B included 14 patients with cerebellar hemispheric tumors; and Group C included 11 patients with cerebellopontine angle (CPA) tumors. More of the 40 patients had BAEP abnormalities (32) than BR abnormalities (24). All of the 11 patients with CPA tumors had some kind of BAEP and BR abnormalities. The 14 patients with cerebellar tumors showed the next most frequent abnormalities: 12 related to the BAEP's and seven to the BR's. The 15 patients with midline tumors showed the least number of abnormalities: nine related to BAEP's and six to the BR's. In the analysis of BAEP wave latencies and interpeak latencies, a wave III latency delay occurred in all groups; latencies of waves IV and V were more significantly delayed in patients with CPA and cerebellar hemispheric tumors, and the interpeak latencies of waves III-V and I-V were markedly prolonged only in patients with CPA tumors (p less than 0.01). In all tumor groups, early response (R1) of BR's was significantly delayed in comparison to a healthy volunteer control group (p less than 0.01), but R1 was more pronounced in cases of CPA tumors when compared with the other tumor groups. Although significant delays in direct and consensual late reflex components (R2) of BR's were noted in comparison to the control group, this delay could not differentiate one tumor group from another. In can be concluded that, while these tests reflect the functions of different cranial nerves and brain-stem tracts, BAEP monitoring is more sensitive than BR testing for the detection of brain-stem involvement in posterior fossa tumors. Cerebellopontine angle tumors almost always cause severe abnormalities in both tests. Cerebellar hemispheric tumors and midline tumors cause fewer changes in both BAEP's and BR's.

Prognostic significance of the electrically elicited blink reflex in neonates

The electrically elicited blink reflex was examined in ten normal neonates, 11 postasphyxial neonates, and 3 congenital hydrocephalus cases. The blink reflex was elicited in all cases. In normal neonates, the latencies and amplitudes were 10.9 +/- 0.7 msec and 159 +/- 62 microV at R1, 34.3 +/- 1.4 msec and 123 +/- 30 microV at R2, and 40.7 +/- 2.3 msec and 84 +/- 25 microV at R'2 respectively. Ischemic-hypoxic brain damage during the neonatal period mainly influenced the late components of the blink reflex. The blink reflex of the postasphyxial neonates showed significantly prolonged latencies of R2 and R'2. The amplitudes were increased in cases with a fair prognosis and decreased in cases with a poor prognosis. A case of congenital hydrocephalus with mental retardation also showed the prolonged latencies of R2 and R'2 in neonatal period. The blink reflex in neonates appears to be useful in predicting the outcome in cases of neonatal asphyxia and congenital hydrocephalus.

Improved preservation of facial nerve function with use of electrical monitoring during removal of acoustic neuromas

Continuous spontaneous electromyographic activity and responses to electrical stimulation of the facial nerve in the surgical field were monitored in 48 patients undergoing primary removal of an acoustic neuroma. The operative and postoperative results in these patients were compared with the results in 48 patients who were matched for age and size of tumor and who underwent the same surgical procedure without intraoperative monitoring. Eighty-three percent of the patients had preoperative evidence of facial neuropathy, which was more severe with larger tumors. Postoperative facial nerve function was most accurately predicted on the basis of the extent of facial neuropathy on preoperative electrophysiologic testing. Anatomic preservation of the facial nerve in patients with large tumors was substantially improved in the monitored patients (67%) in comparison with those without monitoring (33%). No difference was noted in facial nerve function in the two groups of patients immediately postoperatively. By 3 months, the degree of improvement in the monitored group exceeded that in those who were not monitored, particularly in patients with medium-sized and large tumors.

Electrically elicited blink reflex and early acoustic evoked potentials in circumscribed and diffuse brain stem lesions

In the present paper, the function of the brain stem in patients with brain stem lesions of various aetiology is investigated with electrophysiological methods. The clinical observations are supplemented by experimental investigations on cats, in which the blink reflex and the early acoustic evoked potentials were registered during the acute elevation of intracranial pressure. The findings in patients with circumscribed space-occupying lesions in the posterior fossa document that the registration of the BR and the BAEP have a functional diagnostic significance above and beyond the neurological and radiological investigation. In the case of the cerebellar space occupations, specific alterations could not be observed. On the contrary, the alterations of BR and BAEP indicate a general disturbance of brain stem function, possibly as a result of a general increase of intracranial pressure. In cerebellopontine angle tumours, both BR and BAEP showed specific alterations which were usually asymmetrical. The BR changes ipsilateral to the tumour are of major topodiagnostic significance, whereas the alterations of the contralateral potential are especially informative in the registration of BAEP. The alterations of BR and BAEP also allow an appraisal of the localization and extent of the lesion in primary space occupations in the brain stem: A pathological R1 indicates a pontine lesion, whereas pathological R2 responses are found in medullary and in oral pontine and mesencephalic lesions. In contrast to cerebellopontine angle tumours, the BAEP tends to show symmetrical alterations in primary brain stem lesions. The prolongations of interpeak latencies correspond to the brain stem segment concerned, and the same also applies to pathological amplitude reduction and deformations of individual potentials. In patients with localized brain stem damage, the reflex pathway of R2 is discussed on the basis of the BR findings. In contrast to the view held up to now that only structures situated caudal of the facial nucleus area are responsible for the genesis of the R2 response, it is assumed on the basis of our own observations that pontomesencephalic structures rostral to the facial nuclei are also important for the genesis of R2. Registration of BR and BAEP in patients with acute diffuse brain stem damage shows that both methods have a high diagnostic and prognostic value. Isolated damage and combined brain stem lesion can be demonstrated and the course can be followed up. Normalization of pathological findings reflects clinical recovery, and conversely a secondary deterioration indicates the presence of complications.(ABSTRACT TRUNCATED AT 400 WORDS)

The value of brain stem auditory, visual and somatosensory evoked potentials and blink reflexes in the diagnosis of multiple sclerosis

Cervical and cortical somatosensory evoked potentials (SEP) following electrical stimulation of the median nerve and blink reflexes (BR) following electrical stimulation of the supraorbital nerve were recorded in 30 normal subjects aged 20-49 years. Subjects aged 40-49 had longer SEP latencies than subjects aged 20-39 years. A total of 29 slightly affected patients with multiple sclerosis (MS) aged 26-49 years, including four patients without clinical signs (suspected MS) and 19 patients with signs indicating only one lesion (possible MS) were examined by low-rate random-stimulated brain stem auditory (BAEP), checkerboard pattern-reversal visual evoked potentials (VEP), SEP and BR. Abnormal recordings by at least one of the examinations were found in all but three patients, and by all four tests in five patients. In patients with definite or probably MS, demonstration of clinically recognized or subclinical lesions was of minor diagnostic value, in contrast to the importance such findings had in patients with suspected or possible MS. Silent lesions were shown by at least one of the tests in the four suspected and in 13 of the possible MS patients, so these 17 patients could be transferred to a more certain diagnostic category. This reclassification was most often due to the BAEP recording. In patients with spinal signs, the combination of BAEP and VEP recording was sufficiently efficient. In patients with optic neuritis a combination of BAEP and SEP was preferred. No abnormal recordings were found in 15 normal subjects examined by all four tests.

Acute intracranial hypertension and auditory brain-stem responses. Part 3: The effects of posterior fossa mass lesions on brain-stem function

The auditory brain-stem responses (BER's), infratentorial intracranial pressure (ICP), systemic blood pressure (BP), and heart rate were recorded before, during and after expansion of an infratentorial epidural mass in anesthetized cats. Two types of BER's to increasing posterior fossa pressure were noted. In Type 1, there was predominantly suppression of the electrical activity of the auditory nuclei of the upper brain stem (Waves V and IV) and upward transtentorial herniation of the midbrain. In Type 2, the neural activity of the lower brain-stem nuclei (Waves III and II) was affected as well as that of the upper brain stem. There was upward and foraminal impaction of the brain stem and cerebellum which was confirmed by the postmortem brain sections. The change in the amplitudes of BER Waves V and III proved useful in detecting upward transtentorial herniation of the midbrain and foraminal herniation of the cerebellum in acute expanding lesions of the posterior fossa. Medullary paralysis was also detected by observing Wave III.

Blink reflexes in posterior fossa lesions

Blink reflexes obtained by electrical stimulation of the supraorbital nerve and electromyographic recording of the orbicularis oculi muscle proved useful as a preliminary method in diagnosis of lesions of the brainstem and the fifth and seventh cranial nerves, and in differentiating intrinsic lesions of the brainstem from extrinsic ones. It was noted that R1 and R2 reflexes were different in the two types of lesions.

Blink reflex in facial-hypoglossal anastomosis

The blink reflex was investigated in two patients after a facial-hypoglossal anastomosis had been performed. In each case the first component of the blink reflex could be demonstrated with normal latency on the operated side after ipsilateral supraorbital stimulation. These findings give further evidence that the first component of the blink reflex is not monosynaptic in nature. The second component of the blink reflex was distinctly retarded in the first case and was not seen at all in the second case. The second component of the blink reflex is influenced strongly by alteration of the intrabulbar and efferent part of the reflex circuits; it shows some correlation with voluntary motor activity.

Orbicularis oculi reflex and facial muscle electromyography. Pre- and postoperative evaluation of posterior fossa space-occupying lesions

The electrically evoked orbicularis oculi reflex was analyzed in 26 patients with proven posterior fossa space-occupying lesions (11 cerebellopontine angle and 15 cerebellar hemispheric masses). In the former group, although only six had clinical evidence of trigeminal or facial involvement, the reflex analysis showed both nerves to be involved in all. Electromyography (EMG) of the orbicularis oculi showed profound denervation of this muscle while only minimal abnormalities of the masseter were seen. The sensory component of the trigeminal nerve was always more involved than its motor component and this was a reliable guide as to the upward and medial extension of the tumor, especially in the absence of clinical localizing signs. In the 15 patients with cerebellar masses, six with masses located posteriorly and entirely within the confines of the cerebellum had normal studies. In eight, the mass was located anteriorly, and fifth nerve involvement could be detected in all by EMG, although only two patients had clinical evidence of such involvement. One patient with dysfunction of the central reflex arc had EMG evidence of an intraventricular dermoid tumor abutting the pons, later confirmed at surgery. Thus, an invaluable body of diagnostic and prognostic data can be obtained by this nontraumatic and simple electrodiagnostic procedure.

Blink reflex in hemiplegia

An electrophysiological study of the blink reflex was undertaken in 20 normal subjects and in 28 patients complaining of central facial palsy caused by unilateral hemispheral damage. In normal subjects, the latency, amplitude and organization of R1 and R2 responses are well known. Habituation of R2 responses occurred between 1 and 2 c/sec stimulation rate. R1 responses habituated at a higher stimulation rate (5 c/sec). In patients with unilateral hemispheral lesion, our results showed that changes in the blink reflex responses were bilateral. On the hemiplegic side the responses showed a decreased amplitude, while they were facilitated on the "normal" side. However, there was no change in latency of the two components of the reflex, on both sides. On the other hand, habituation of the late component occurred on the hemiplegic side for low stimulation rates: (0.5--1 c/sec), while on the "normal" side there was less habituation (3--4 c/sec), as compared with normal subjects. These results agree with those of experimental studies on cortical modulatory influences on brain-stem nuclei. They suggest a tactile origin of the two components of the blink reflex.

[Orbicularis oculi reflex after facial paralysis: decreased amplitude of reflex response and spreading to all hemifacial muscles after reinnervation (author's transl)]

After the acute stage of peripheral facial paralysis with nerve degeneration we find some signs of paresis after reinnervation due to insufficient motor recovery and associated movements due to faulty reinnervation. Electromyographical investigation of the orbicularis oculi reflex can be used for the objective evaluation of these two phenomena. This shows the following typical signs: 1. The amplitudes of the early and late reflex response are decreased on the affected side proportionate to the degree of paresis. 2. The response occurs in all reinnervated hemifacial muscles as a result of misdirection of fibres which originally innervated the orbicularis oculi muscle.