Simultaneous custom-made replacement of the temporomandibular joint and cranioplasty.

A 23-year-old man presented with a history of fibrous ankylosis of the left temporomandibular joint (TMJ), scarring and shortening of the left temporalis muscle secondary to transection, and surgically-induced neuropathic pain after previous decompression of the temporal bone. There was evident hollowing of the left temporal fossa, and mouth opening was limited to 5mm. The aims of the operation were to treat the ankylosis, improve cosmesis, and reduce his medication. His left TMJ was reconstructed with a custom-made alloplastic joint, and a simultaneous custom-made cranioplasty. At follow-up after 2 years he was free of pain and taking no drugs. He had no obvious cranial deformity, and his mouth opening had increased to 35 mm. To our knowledge this is the first reported case of simultaneous custom-made cranioplasty and reconstruction of the TMJ.

External ventricular drain infection: the effect of a strict protocol on infection rates and a review of the literature.

External ventricular drains (EVDs), like any surgically-implanted foreign body, are at risk of infection. We present the results of a completed audit loop following introduction of an evidence-based protocol for their insertion and management. There were two phases over a 2-year period. Phase 1 was a retrospective audit of our EVD infection rate. Phase 2 was a prospective audit of the infection rate subsequent to the introduction of a protocol for the insertion and management of EVDs. In phase 1, the infection rate was 27%. In phase 2, the infection rate was 12%. This was a statistically significant reduction (p < 0.05, Chi-squared test). EVD infection is unfortunately a common clinical problem and associated with potential morbidity and mortality. This study demonstrates that adherence to an evidence-based protocol for their insertion and management is associated with a significant reduction in the infection rate.

Awake stereotactic biopsy of brain stem lesions: technique and results.

BACKGROUND: Brain stem lesions are a heterogenous pathological group. In adults, pre-operative radiological diagnoses prove to be wrong in 10 to 20% of cases. It is therefore imperative to have a tissue diagnosis for appropriate therapeutic measures. Unless these lesions have a sizeable exophytic component, open biopsy and/or resection is marred by low diagnostic yield and prohibitive mortality/morbidity rates. METHODS: We describe our experience with awake stereotactic biopsy of brain stem lesions. Keeping the patient awake and monitoring clinically during the procedure allows us to make necessary changes in the trajectory of the biopsy probe to minimize the morbidity. A series of 13 brain stem lesions were stereotactically biopsied using CT guidance. Seven had midbrain lesions; four had pontine and two had Ponto-medullary lesions. A frontal, pre-coronal, transcortical trajectory was used in all patients. FINDINGS: Histological diagnosis was established in all but one patient. There was no procedural mortality, and morbidity was minimal and temporary, occurring in three patients. CONCLUSION: Awake stereotactic biopsy is a safe technique when combined with clinical monitoring.

Externalising deep brain electrodes: an increased risk of infection?

It is the practice in many centres to externalise deep brain electrodes in functional neurosurgery to confirm efficacy of therapy prior to full implantation of the pacemaker. It has been a concern that such practice might lead to an increased rate of infection. We report a retrospective study of the rates of infection in two major centres where all electrodes are externalised in one centre and directly implanted in the other. We have not found an increased rate of infection as a result of externalisation and feel, particularly in pain patients, that doing so can lead to significant cost savings by avoiding ineffective implantations.

Ocular microtremor: a tool for measuring depth of anaesthesia?

Ocular microtremor (OMT) is a fine high frequency tremor of the eyes caused by extra-ocular muscle activity stimulated by impulses emanating in the brain stem. Several studies have shown that the frequency of this tremor is reduced in patients whose consciousness is reduced by anaesthesia or head injury. Therefore, OMT may possibly be used to determine depth of anaesthesia. Twenty-two unpre-medicated subjects undergoing surgery with general anaesthesia were studied. OMT activity was measured at admission using the open eye piezoelectric strain gauge technique. Anaesthesia was induced with propofol using a target controlled infusion delivery system (Diprifusor). OMT activity was then recorded at predicted plasma propofol concentrations of 1, 2, 3 and 5 microg ml(-1). The patient's level of consciousness (response to command or stimulation) was assessed after each OMT measurement. OMT activity was reduced progressively at predicted plasma concentrations of propofol of I and 2 microg ml(-1) and then plateaued between 3 and 5 microg ml(-1). There was a significant difference between the last awake OMT recording and the first recording at loss of consciousness (P < 0.001). OMT recording holds promise as a practical indicator of the depth of anaesthesia.

Effect of age on ocular microtremor activity.

BACKGROUND: Ocular microtremor (OMT) is a high-frequency tremor of the eyes. It is present in all individuals and is related to brainstem activity. The OMT signal appears as an irregular oscillatory movement with intermittent burst-like components. The clinical interest in OMT has centered on its use in the assessment of the comatose patient, with broad agreement among authors of its prognostic value. The purpose of this study was to examine the changes in OMT activity related to aging. METHODS: OMT was recorded from 72 normal healthy subjects using the piezoelectric strain gauge technique. The subjects ranged in age from 21 to 88 years (54.22 +/- 20.43 years, mean +/- SD). RESULTS: Our results show that the overall frequency and frequency content of the bursts falls with age (p < .002 and p < .001, respectively). There is a highly significant drop in all three frequency parameters of OMT (p < .0001) in subjects older than 60 years of age. CONCLUSIONS: These results suggest that different values of normality should operate for subjects over 60 years of age when considering the clinical application of OMT.

Ocular microtremor (OMT): a new neurophysiological approach to multiple sclerosis.

Using a piezoelectric transducer, the frequency and pattern of ocular microtremor (OMT) between 50 normal subjects and 50 patients with multiple sclerosis were compared. Controls were age matched. All records were analysed blindly. The frequency of OMT in the normal group was 86 (SD 6) Hz, which was significantly different from that of the multiple sclerosis group (71 (SD) 10 Hz, p<0.001). Those in the multiple sclerosis group with clinical evidence of brain stem or cerebellar disease (n=36) had an average OMT frequency of 67 (SD 9) Hz (p<0.001) compared with normal (n=86), whereas those with no evidence of brain stem or cerebellar involvement (n=14) had a frequency of 81.2 (SD 6) Hz (p<0.05, n=64). The differences between the two multiple sclerosis groups were also significant (p<0. 001, n=50). At least one abnormality (frequency and pattern) of OMT activity was seen in 78% of patients with multiple sclerosis. In the presence of brain stem or cerebellar disease 89% had abnormal records whereas in the absence of such disease 50% had abnormal records. This is the first report of the application of this technique to patients with multiple sclerosis. The results suggest that OMT activity may be of value in the assessment of multiple sclerosis.

Ocular microtremor in brain stem death

OBJECTIVE: This study was undertaken to establish whether measurement of ocular microtremor (OMT) activity could be used as a method to establish brain stem death. Presently, the diagnosis of brain stem death can be made using clinical criteria alone. OMT is a high-frequency, low-amplitude physiological tremor of the eye caused by impulses emanating from the brain stem. There have been a number of reports indicating that the recording of OMT may be useful in the assessment of comatose states and in establishing brain stem viability or death. METHODS: We obtained the OMT recordings of 32 patients suspected of having brain stem death using the piezoelectric strain gauge technique. This method involves mounting the piezoelectric probe in a headset and lowering the rubber-tipped end piece onto the anesthetized scleral surface of the subject. The signal produced is recorded on audiomagnetic tape and later played back and analyzed on an electrocardiographic tape analyzer. RESULTS: In 28 patients, initial clinical assessment confirmed the diagnosis of brain stem death and no OMT activity was recorded from these subjects. In three patients in whom initial clinical assessment demonstrated brain stem function, OMT activity was present; when brain stem death was subsequently diagnosed in these three patients, no OMT activity could be demonstrated. In the remaining patient, two of three OMT recordings demonstrated activity in spite of the absence of clinical evidence of brain stem function. A post mortem revealed bacterial cerebritis in this subject. CONCLUSION: The results suggest that OMT is a sensitive method of detecting brain stem life and that it could play an important role in the assessment of brain stem death.

Dominant frequency content of ocular microtremor from normal subjects.

Ocular microtremor (OMT) is a high frequency tremor of the eyes present during fixation and probably related to brainstem activity (Coakley, D. (1983). Minute eye movement and brain stem function. CRC Press, FL.). Published observations on the frequency of OMT have varied widely. Ocular microtremor was recorded in 105 normal healthy subjects using the Piezoelectric strain gauge technique. The dominant frequency content of a signal was determined using the peak counting method. Values recorded ranged from 70 to 103 Hz, the mean frequency being 83.68 Hz (S.D. +/- 5.78 Hz).

Ocular microtremor in patients with idiopathic Parkinson's disease.

Abnormalities in the oculomotor control mechanism of patients with idiopathic Parkinson's disease are well recognised. In this study the effect of Parkinson's disease on tonic output from oculomotor nuclei was studied by using oculomicrotremor as an index of such output. Oculomicrotremor readings were taken from 22 parkinsonian patients and 22 normal healthy volunteers using the piezoelectric strain gauge technique. There was a slower overall tremor frequency, baseline, and burst frequency in the parkinsonian group. There was also a significant increase in the duration of baseline, with a decrease in the number of bursts a second and a decrease in average duration of bursts in the patient group compared with the normal group. One patient, whose medication was withdrawn, showed a marked decrease in mean frequency and baseline frequency with a decrease in number of bursts and increase in baseline duration compared with readings taken when treatment recommenced. These results suggest that variables measured in oculomicrotremor are altered compared with normal subjects, reflecting altered tonic output from oculomotor nuclei in patients with idiopathic Parkinson's disease.

Ocular microtremor in oculomotor palsy.

OBJECTIVES: Ocular microtremor (OMT) is a high frequency tremor of the eyes present in all individuals. Recent reports suggest that OMT may be a useful indicator of brainstem function. However, the actual origin of ocular microtremor remains controversial. This study aims to provide evidence that OMT has a neurogenic origin. MATERIALS AND METHODS: The OMT activity of five subjects with unilateral oculomotor nerve palsy and one subject with complete unilateral internal and external ophthalmoplegia were recorded from both eyes of each subject using the piezoelectric strain gauge technique, with the normal eye acting as a control. Five parameters of OMT activity were studied in each subject: the peak count, the power of the high frequency peak, the percentage power between 60 and 100 Hz, the percentage power between 70 and 80 Hz, and the 10 dB cut-off point. RESULTS: In the five subjects with oculomotor nerve palsy, the mean peak count in the normal eye was 88.4 Hz (SD+/-16.9) and in the affected eye was 59 Hz (SD+/-8.6), P < 0.0096. There was also a fall in the peak power, the power between 60 and 100 Hz, and the power between 70 and 80 Hz. In subject six, who had complete opthalmoplegia, there was no evidence of OMT activity in the denervated eye. CONCLUSIONS: These results suggest that innervation of the extraocular muscles is necessary for normal OMT activity, and OMT therefore has a neurogenic origin.