[Rectus muscle transposition for the treatment of complex ocular motility disorders]

BACKGROUND

Transposition techniques alter the muscle paths thereby creating new directions of muscle force. Extraocular muscle transposition procedures have been used to treat abducens palsy, Duane's retraction syndrome, double-elevator palsy and other complex ocular motility abnormalities. The purpose of this study was to evaluate the surgical and functional results of rectus muscle transposition in patients with different aetiologies of severe ocular motility deficits.

PATIENTS AND METHODS

Between 1992 and 2008 rectus muscle transposition surgery has been performed on 31 patients. In this retrospective case series one patient with an abducens nerve palsy is presented as an example. In addition, six patients with motility disorders of different aetiologies who had transposition manoeuvers were evaluated. Preoperative, surgical and postoperative data are reported.

RESULTS

Rectus muscle transposition has been performed because of severe functional loss of the lateral rectus muscle, the superior rectus muscle or the medial rectus muscle as well as in myopic strabismus fixus. One of the patients had traumatic sixth nerve palsy. The underlying pathology in patients who had superior transposition of the horizontal rectus muscles were double-elevator palsy, congenital oculomotor nerve palsy and hypotropia caused by sphenoid wing hypoplasia. A nasal transposition of the vertical rectus muscles was performed in traumatic and tumour-associated muscle loss of the medial rectus muscle. The large preoperative deviations were markedly reduced postoperatively and even ocular motility partially improved.

CONCLUSIONS

Transposition surgery seems to be a suitable procedure for the treatment of complex ocular motility disorders. In cases of a complete lack of function of an extraocular muscle or in complex, uncommon conditions, which are difficult to treat with any other surgery, muscle transposition seems to be an effective procedure.

[Long-term follow-up after surgery for exodeviation]

BACKGROUND

In strabismus surgery the challenge is the preoperative determination of the surgical dosage. We assessed the long-term follow-up after strabismus surgery for exodeviations and evaluated the employed dosage.

PATIENTS AND METHODS

We present a study of 53 consecutive patients who underwent surgery for exodeviations. One year postoperative results were analysed based on strict criteria. Out of the original group of 53 patients we could evaluate the long-term follow-up in 18 patients, after an average period of 13 years. The criteria for patients with intermittent exotropia and decompensating exophoria after one year and in the long-term follow-up were determined as follows: very good: orthophoria or orthotropia with exo- or esophoria less than 5 PD; good: orthotropia with exo- or esotropia less than 10 PD; satisfactory: orthotropia with exo- or esophoria > 10 PD but less than the preoperative angle; bad: constant eso- or exotropia or > preoperative angle. For patients with a constant divergent strabismus the following criteria were determined: very good: orthophoria or orthotropia with exo- or esophoria less than 5 PD; good: exo- or esophoria less than 10 PD or tropia of 5 degrees (microstrabismus); satisfactory: exo- or esophoria > 10 PD or exo- or esotropia > 10 PD but < preoperative angle; bad: same as preoperative or more. A subgroup analysis of 41 patients who underwent monolateral combined rectus muscle surgery was performed regarding their long-term follow-up (average: 13 years) as well. Concurrently the patients completed a questionnaire.

RESULTS

One year postoperatively 6 outcomes were very good, 14 good, 31 satisfactory and 2 were poor. On average 13 years postoperatively the same patients were evaluated based on the same strict criteria. No outcome was very good, 4 good, 12 satisfactory and 2 were poor. The judgement of the patients in the questionnaire was at both times clearly better. The exo-shift in the first postoperative year was 3.5 degrees , in the next on average 12 years the mean divergent strabismus angle increased by another 2.9 degrees.

CONCLUSIONS

The outcome evaluation after a long-term follow-up showed amazingly stable results compared to the follow-up after one year. With a more aggressive dosage we could have achieved more orthophoric results, but also more undesirable overcorrections.

Stereotactic interstitial radiosurgery for intracranial Rosai-Dorfman disease. A novel therapeutic approach

BACKGROUND

Rosai-Dorfman disease is an idiopathic, histoproliferative disorder characterized by massive painless lymphadenopathy. The favorable treatment of Rosai-Dorfman disease affecting the central nervous system is surgical resection. Histological and immunohistochemical confirmation is essential for a definitive diagnosis.

CASE REPORT

The authors report on a 10-year-old patient with Rosai-Dorfman disease of the central nervous system who presented with increased intracranial pressure. She was treated by stereotactic interstitial irradiation using iodine-125 seeds (interstitial radiosurgery).

RESULT

Stereotactic surgery was performed without complications. The patient recovered well to a normal neurologic status. MR images showed a complete remission 49 months after treatment.

CONCLUSION

The presented case demonstrates the high efficacy and safety of interstitial irradiation for intracranial Rosai-Dorfman disease. Hence, interstitial radiosurgery could be an appropriate therapeutic option for high-risk resectable intracranial Rosai-Dorfman disease.

Long-term follow-up of children with benign abducens nerve palsy

PURPOSE

Benign abducens nerve palsy is rare in childhood. Diagnosis is made by exclusion, and the severe underlying pathologies have to be ruled out. The aim of our study was to present the largest single-center series of patients with the longest period of follow-up to confirm the benign nature of this entity.

PATIENTS AND METHODS

We carried out a retrospective study of 12 consecutive children with benign abducens nerve palsy. All children underwent a careful orthoptic and ophthalmic examination during acute presentation and follow-up.

RESULTS

Painless palsies were associated with a preceding infection or immunization in five patients. The left eye was affected in nine children and no bilateral case was found. No sex differences were seen. Recovery was observed within 6 months in all cases, and ipsilateral recurrences occurred in three children. Three children required strabismus surgery. None of the patients developed long-term recurrences or neurological abnormalities during a mean follow-up of more than 9 years.

CONCLUSIONS

Our data support earlier findings, such as painless and predominately left-sided occurrence, spontaneous recovery within 6 months, and ipsilateral recurrence. In contrast to much of the literature, we did not find a female preponderance. Exclusion of severe causes and close follow-up is mandatory for these patients. As none of the patients developed long-term recurrences or neurological sequelae, this entity can be regarded as a benign condition without malignant associations or complications.

Characterisation of tremor-associated local field potentials in the subthalamic nucleus in Parkinson's disease

We simultaneously recorded local field potentials (LFPs) in the subthalamic nucleus (STN) and surface electromyographic signals (EMGs) from the extensor and flexor muscles of the contralateral forearm in eight patients with idiopathic tremor-dominant Parkinson's disease (resting tremor) during the bilateral implantation of deep brain stimulation electrodes. Recordings were made at different heights (in 0.5- to 2.0-mm steps beginning outside the STN) using up to five concentrically configured macroelectrodes (2 mm apart). The patients were instructed to relax their contralateral forearm (rest condition). We analysed the coherence between tremor EMGs and STN LFPs, which showed significant tremor-associated coupling at single tremor and double tremor frequencies. Moreover, the EMG-LFP coherences were characterised by differences between antagonistic muscles (flexor, extensor) and by the spatial distribution of LFPs within the STN. Coherence at single and double tremor frequencies occurred significantly more frequently within STN than above STN (in the zona incerta). In this study, we were able to show that, within STN, tremor-associated LFP activity varied with spatial distribution and with the contralateral antagonistic forearm muscles. These findings suggest the existence of distribution- and muscle-specific tremor-associated LFP activity at different tremor frequencies and an organisation of tremor-related subloops within the STN.

Remission of alcohol dependency following deep brain stimulation of the nucleus accumbens: valuable therapeutic implications?

Chronic consumption of alcohol represents one of the greatest health and socioeconomic problems worldwide. We report on a 54-year-old patient with a severe anxiety disorder and secondary depressive disorder in whom bilateral deep brain stimulation (DBS) of the nucleus accumbens was carried out. Despite the absence of desired improvement in his primary disorder, we observed a remarkable although not primarily intended alleviation of the patient's comorbid alcohol dependency. Our case report demonstrates the extremely effective treatment of alcohol dependency by means of DBS of the nucleus accumbens and may reveal new prospects in overcoming therapy resistance in dependencies in general.

Observations on unaided smoking cessation after deep brain stimulation of the nucleus accumbens

AIMS

We explore whether clinical research on deep brain stimulation (DBS) of the nucleus accumbens (NAc) to treat addiction is justified besides theoretical speculation.

METHODS

Since 2004, 10 patients who were also smokers were treated at the University of Cologne for Tourette's syndrome (TS), obsessive-compulsive disorders (OCD) or anxiety disorders (AD) by DBS of the NAc. We assessed their smoking behavior after DBS and (in retrospection) before by the Fagerstrom Test for Nicotine Dependence (FTND) and additional items.

RESULTS

Three male patients were able to quit smoking after DBS. They were less dependent and higher motivated compared to the rest of the sample. They are stimulated with a higher voltage. During 1-year, 2-year, and 30-month follow-ups, we found a higher rate of successful smoking cessation (20, 30 and 30%) compared to unaided smoking cessation in the general population (13, 19 and 8.7%).

CONCLUSIONS

Albeit the results of the study are severely limited by the method of retrospective self-assessment of psychiatric patients, further research of DBS of the NAc to treat addiction seems justified. In addition to biological mediators, psychosocial factors should be assessed in further prospective studies.

Tremor entrainment by patterned low-frequency stimulation

High-frequency test stimulation for tremor suppression is a standard procedure for functional target localization during deep brain stimulation. This method does not work in cases where tremor vanishes intraoperatively, for example, due to general anaesthesia or due to an insertional effect. To overcome this difficulty, we developed a stimulation technique that effectively evokes tremor in a well-defined and quantifiable manner. For this, we used patterned low-frequency stimulation (PLFS), i.e. brief high-frequency pulse trains administered at pulse rates similar to neurons' preferred burst frequency. Unlike periodic single-pulse stimulation, PLFS enables one to convey effective and considerably greater integral charge densities without violation of safety requirements. In a computational investigation of an oscillatory neuronal network temporarily rendered inactive, we found that PLFS evokes synchronized activity, phase locked to the stimulus. While a stronger increase in the amount of synchrony in the neuronal population requires higher stimulus intensities, the portion of synchronously active neurons nevertheless becomes strongly phase locked to PLFS already at weak stimulus intensities. The phase entrainment effect of PLFS turned out to be robust against variations in the stimulation frequency, whereas enhancement of synchrony required precisely tuned stimulation frequencies. We applied PLFS to a patient with spinocerebellar ataxia type 2 (SCA2) with pronounced tremor that disappeared intraoperatively under general anaesthesia. In accordance with our computational results, PLFS evoked tremor, phase locked to the stimulus. In particular, weak PLFS caused low-amplitude, but strongly phase-locked tremor. PLFS test stimulations provided the only functional information about target localization. Optimal target point selection was confirmed by excellent post-operative tremor suppression.

STN-DBS activates the target area in Parkinson disease: an FDG-PET study

OBJECTIVE

The immediate effects of deep brain stimulation (DBS) on subcortical neurons of its target region are controversial.

METHODS

We measured the regional normalized resting cerebral metabolic rate of glucose (nCMRGlc) with 18-fluorodeoxyglucose (FDG) and PET in 12 patients with Parkinson disease (PD) and bilateral DBS of the subthalamic nucleus (STN) compared to 10 age-matched controls. PET was performed before surgery and 6 months after electrode implantation in DBS off- and on-conditions. Stereotactic coordinates of active STN electrode poles were determined with intraoperative skull x-ray and transferred to preoperative MR images. Subsequently, volumes of interest (VOIs) were placed around active electrode contacts, in the STN and in the globus pallidus. DBS induced changes of nCMRGlc values were determined in each VOI after PET and MRI coregistration.

RESULTS

Electrode placement without stimulation led to significant FDG uptake reduction in the electrode region and in the STN (microlesional effect). Under active DBS, the local nCMRGlc significantly increased in all VOIs under investigation.

CONCLUSIONS

The data demonstrate that deep brain stimulation (DBS) induced metabolic activation of the subthalamic region and the directly connected globus pallidus which is in line with local and remote excitation of neurons by high frequency stimulation. These PET findings most likely reflect tonic driving of the DBS target area and its projection sites via ortho- and antidromic fiber conduction. We conclude that subthalamic nucleus DBS has predominant excitatory properties and does, therefore, fundamentally differ from lesional neurosurgery.

Contribution of subcortical structures to cognition assessed with invasive electrophysiology in humans

Implantation of deep brain stimulation (DBS) electrodes via stereotactic neurosurgery has become a standard procedure for the treatment of Parkinson's disease. More recently, the range of neuropsychiatric conditions and the possible target structures suitable for DBS have greatly increased. The former include obsessive compulsive disease, depression, obesity, tremor, dystonia, Tourette's syndrome and cluster-headache. In this article we argue that several of the target structures for DBS (nucleus accumbens, posterior inferior hypothalamus, nucleus subthalamicus, nuclei in the thalamus, globus pallidus internus, nucleus pedunculopontinus) are located at strategic positions within brain circuits related to motivational behaviors, learning, and motor regulation. Recording from DBS electrodes either during the operation or post-operatively from externalized leads while the patient is performing cognitive tasks tapping the functions of the respective circuits provides a new window on the brain mechanisms underlying these functions. This is exemplified by a study of a patient suffering from obsessive-compulsive disease from whom we recorded in a flanker task designed to assess action monitoring processes while he received a DBS electrode in the right nucleus accumbens. Clear error-related modulations were obtained from the target structure, demonstrating a role of the nucleus accumbens in action monitoring. Based on recent conceptualizations of several different functional loops and on neuroimaging results we suggest further lines of research using this new window on brain functions.

Neuropsychological and psychiatric changes after deep brain stimulation for Parkinson's disease: a randomised, multicentre study

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) reduces motor symptoms in patients with Parkinson's disease (PD) and improves their quality of life; however, the effect of DBS on cognitive functions and its psychiatric side-effects are still controversial. To assess the neuropsychiatric consequences of DBS in patients with PD we did an ancillary protocol as part of a randomised study that compared DBS with the best medical treatment.

METHODS

156 patients with advanced Parkinson's disease and motor fluctuations were randomly assigned to have DBS of the STN or the best medical treatment for PD according to the German Society of Neurology guidelines. 123 patients had neuropsychological and psychiatric examinations to assess the changes between baseline and after 6 months. The primary outcome was the comparison of the effect of DBS with the best medical treatment on overall cognitive functioning (Mattis dementia rating scale). Secondary outcomes were the effects on executive function, depression, anxiety, psychiatric status, manic symptoms, and quality of life. Analysis was per protocol. The study is registered at ClinicalTrials.gov, number NCT00196911.

FINDINGS

60 patients were randomly assigned to receive STN-DBS and 63 patients to have best medical treatment. After 6 months, impairments were seen in executive function (difference of changes [DBS-best medical treatment] in verbal fluency [semantic] -4.50 points, 95% CI -8.07 to -0.93, Cohen's d=-;0.4; verbal fluency [phonemic] -3.06 points, -5.50 to -0.62, -0.5; Stroop 2 naming colour error rate -0.37 points, -0.73 to 0.00, -0.4; Stroop 3 word reading time -5.17 s, -8.82 to -1.52, -0.5; Stroop 4 colour naming time -13.00 s, -25.12 to -0.89, -0.4), irrespective of the improvement in quality of life (difference of changes in PDQ-39 10.16 points, 5.45 to 14.87, 0.6; SF-36 physical 16.55 points, 10.89 to 22.21, 0.9; SF-36 psychological 9.74 points, 2.18 to 17.29, 0.5). Anxiety was reduced in the DBS group compared with the medication group (difference of changes in Beck anxiety inventory 10.43 points, 6.08 to 14.78, 0.8). Ten patients in the DBS group and eight patients in the best medical treatment group had severe psychiatric adverse events.

INTERPRETATION

DBS of the STN does not reduce overall cognition or affectivity, although there is a selective decrease in frontal cognitive functions and an improvement in anxiety in patients after the treatment. These changes do not affect improvements in quality of life. DBS of the STN is safe with respect to neuropsychological and psychiatric effects in carefully selected patients during a 6-month follow-up period.

FUNDING

German Federal Ministry of Education and Research (01GI0201).

[Sinusitis and ocular motility disorders]

BACKGROUND

Secondary inflammatory orbital involvement due to acute or chronic sinusitis is common. The pneumatized system of the paranasal sinuses is abut to the bones of the orbit in up to 80 percent, therefore the association is a seductive theory due to their anatomic closeness. Typically, sinusitis can influence ocular motility by affecting single muscles or a combination of muscles/cranial nerves due to a local inflammatory tissue reaction. The expected picture would be a more or less complex restriction of eye movements.

PATIENTS AND METHODS

In this case study nine consecutive patients were prospectively included between January 2006 and August 2007.

RESULTS

Five of the patients did not experience any motility disorder, the other four had a restricted motility. Case reports of the four patients are presented to demonstrate the range of ocular motility disorders related to sinusitis.

CONCLUSIONS

Orbital complications due to sinusitis include motility disorders among others. They can even cause orbital sepsis and cavernous sinus thrombosis. On the one hand sinusitis can affect almost the whole spectrum of ocular motility disorders, on the other hand it may mask a dangerous cerebral aneurysm. The "close-lying" connections, as seductive they are, should not divert from the rule: infrequent causes are infrequent and frequent causes are frequent!