[Towards a positive physiological definition of the deep brain nuclei in humans]

INTRODUCTION

Using microelectrodes for recording purposes in deep brain stimulation (DBS) has proven to be very useful. Their efficiency can be improved by characterising the properties of extracellular action potentials (EAPs).

PATIENTS AND METHODS

We analysed the records of nine patients who underwent surgery for epilepsy or aggressiveness under general anaesthesia. The properties of the EAPs of the centromedian, ventral intermediate, ventrocaudal and posteromedial hypothalamic nuclei of the thalamus have been determined.

RESULTS

We have analysed 706 thalamic and 142 hypothalamic cells. The proportion of cell types was found to be specific to each cell nucleus. The most frequent cell type was P1P2N1 (59.5%), followed by N1P1N2 (23.1%). The first phase of the EAP is highly variable. The properties of the EAP phases of the same morphology differ greatly from one nucleus to another.

CONCLUSIONS

We have shown that several deep brain nuclei have properties that are specific to the morphology of the EAPs. This will allow for improved localisation of these nuclei during DBS.

Patients awaiting surgery for neurosurgical diseases during the first wave of the COVID-19 pandemic in Spain: a multicentre cohort study

OBJECTIVES

The large number of infected patients requiring mechanical ventilation has led to the postponement of scheduled neurosurgical procedures during the first wave of the COVID-19 pandemic. The aims of this study were to investigate the factors that influence the decision to postpone scheduled neurosurgical procedures and to evaluate the effect of the restriction in scheduled surgery adopted to deal with the first outbreak of the COVID-19 pandemic in Spain on the outcome of patients awaiting surgery.

DESIGN

This was an observational retrospective study.

SETTINGS

A tertiary-level multicentre study of neurosurgery activity between 1 March and 30 June 2020.

PARTICIPANTS

A total of 680 patients awaiting any scheduled neurosurgical procedure were enrolled. 470 patients (69.1%) were awaiting surgery because of spine degenerative disease, 86 patients (12.6%) due to functional disorders, 58 patients (8.5%) due to brain or spine tumours, 25 patients (3.7%) due to cerebrospinal fluid (CSF) disorders and 17 patients (2.5%) due to cerebrovascular disease.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was mortality due to any reason and any deterioration of the specific neurosurgical condition. Second, we analysed the rate of confirmed SARS-CoV-2 infection.

RESULTS

More than one-quarter of patients experienced clinical or radiological deterioration. The rate of worsening was higher among patients with functional (39.5%) or CSF disorders (40%). Two patients died (0.4%) during the waiting period, both because of a concurrent disease. We performed a multivariate logistic regression analysis to determine independent covariates associated with maintaining the surgical indication. We found that community SARS-CoV-2 incidence (OR=1.011, p<0.001), degenerative spine (OR=0.296, p=0.027) and expedited indications (OR=6.095, p<0.001) were independent factors for being operated on during the pandemic.

CONCLUSIONS

Patients awaiting neurosurgery experienced significant collateral damage even when they were considered for scheduled procedures.

Deep brain stimulation in Parkinson's disease: analysis of brain fractional anisotropy differences in operated patients

INTRODUCTION

Deep brain stimulation (DBS) of the subthalamic nucleus is currently an evidence-based therapeutic option for motor symptoms in patients with Parkinson's disease (PD), although other non-motor symptoms can be affected by stimulation.

AIM

Our objective is to evaluate the global changes in the connectivity of the large-scale structural network in PD patients that have obtained a benefit from subthalamic DBS.

SUBJECTS AND METHODS

Retrospective study of 31 subjects: 7 PD patients with subthalamic DBS (group A), 12 age and gender-matched non-operated PD (B) and 12 healthy controls (C). All subjects had undergone a 1.5 T brain MRI with DTI. DICOM images were processed with the FSL5.0 software and TBSS tool.

RESULTS

The study group comprised 23 men and 8 women. No statistically significant differences in age, gender, scores on the HandY scale and mean follow-up between group A and B were found, and in age and gender between groups A and C. Statistical analysis revealed differences in the fractional anisotropy of the different groups in certain areas: bilateral corticospinal tract, anterior thalamic radiations, bilateral fronto-occipital fascicle, both superior longitudinal fascicles, and left inferior longitudinal fascicle.

CONCLUSIONS

In our series, PD patients treated with bilateral subthalamic DBS showed a significantly higher fractional anisotropy in widespread areas of the cerebral white matter; suggesting that neuromodulation produces connectivity changes in different neural networks.

[Deep brain stimulation in drug-resistant epilepsy]

INTRODUCTION

Deep brain stimulation (DBS) in drug-resistant epilepsy has been applied to several brain targets. However, its exact mechanism of action is not known, and the diversity of targets makes it difficult to know the degree of evidence that supports its use.

DEVELOPMENT

A review of the literature on DBS for drug-resistant epilepsy was conducted. The efficacy of DBS in drug-resistant epilepsy seems to be mediated by a desynchronisation of neuronal activity at the epileptogenic focus or a modulation of the «circuitopathies» that exist in epilepsy, depending on the target. In DBS multiple cortical and subcortical structures have been used, but class I evidence exists only for DBS of the anterior nucleus of the thalamus.

CONCLUSIONS

DBS in epilepsy is still under investigation, with class I evidence for DBS of the anterior nucleus of the thalamus. The rest of the targets have yielded variable results that must be confirmed with randomised designs in larger series.

Language hemispheric dominance analyzed with magnetic resonance DTI: correlation with the Wada test

OBJECTIVE

Language lateralization is a major concern in some patients with pharmacoresistant epilepsy who will face surgery; in these patients, hemispheric dominance testing is essential to avoid further complications. The Wada test is considered the gold standard examination for language localization, but is invasive and requires many human and material resources. Functional MRI and tractography with diffusion tensor imaging (DTI) have demonstrated that they could be useful for locating language in epilepsy surgery, but there is no evidence of the correlation between the Wada test and DTI MRI in language dominance.

METHODS

The authors performed a retrospective review of patients who underwent a Wada test before epilepsy surgery at their institution from 2012 to 2017. The authors retrospectively analyzed fractional anisotropy (FA), number and length of fibers, and volume of the arcuate fasciculus and uncinate fasciculus, comparing dominant and nondominant hemispheres.

RESULTS

Ten patients with temporal lobe epilepsy were reviewed. Statistical analysis showed that the mean FA of the arcuate fasciculus in the dominant hemisphere was higher than in the nondominant hemisphere (0.369 vs 0.329, p = 0.049). Also, the number of fibers in the arcuate fasciculus was greater in the dominant hemisphere (881.5 vs 305.4, p = 0.003). However, no differences were found in the FA of the uncinate fasciculus or number of fibers between hemispheres. The length of fibers of the uncinate fasciculus was longer in the dominant side (74.4 vs 50.1 mm, p = 0.05). Volume in both bundles was more prominent in the dominant hemisphere (12.12 vs 6.48 cm3, p = 0.004, in the arcuate fasciculus, and 8.41 vs 4.16 cm3, p = 0.018, in the uncinate fasciculus). Finally, these parameters were compared in patients in whom the seizure focus was situated in the dominant hemisphere: FA (0.37 vs 0.30, p = 0.05), number of fibers (114.4 vs 315.6, p = 0.014), and volume (12.58 vs 5.88 cm3, p = 0.035) in the arcuate fasciculus were found to be statistically significantly higher in the dominant hemispheres. Linear discriminant analysis of FA, number of fibers, and volume of the arcuate fasciculus showed a correct discrimination in 80% of patients (p = 0.024).

CONCLUSIONS

The analysis of the arcuate fasciculus and other tract bundles by DTI could be a useful tool for language location testing in the preoperative study of patients with refractory epilepsy.

[Bases of deep brain stimulation]

INTRODUCTION

Deep brain stimulation is an effective therapy that is being used in an increasing number of indications. The mechanisms by which it exerts its therapeutic effect are still largely unknown, although there is increasing evidence of its influence at various levels.

AIM

To review the existing literature on the mechanism of action of deep brain stimulation.

DEVELOPMENT

Deep brain stimulation acts on brain tissue that is stimulated at various levels: molecular, cellular and neural networks. Spatial, temporal and electrical factors are involved in its effectiveness, but it mainly seems to perform its function by replacing anomalous firing patterns, which are present in certain neurological and psychiatric diseases. Other mechanisms, such as neuroprotection or neurogenesis, remain under study.

CONCLUSIONS

Although many of the effects by which deep brain stimulation acts on the brain are still unknown, it seems to be a complex treatment, with large-scale effects, in which the correction of circuitopathies seems to prevail as the main mechanism.

[Myelopathy secondary to an aneurysmal bone cyst of thoracic spine]

INTRODUCTION

Spinal aneurysmal bone cysts are very infrequent benign osteolytic lesions consisting of blood-filled cavities that are separated by osteo-connective septa and osteoclast-type giant cells. Clinically they manifest with local pain, neurological symptoms secondary to spinal cord compression, and fractures, deformities and vertebral instability. We report a case of an aneurysmal bone cyst in the thoracic spine with neurological signs and symptoms treated by means of a full microsurgical resection, with no associated neurological sequelae.

CASE REPORT

A 47-year-old woman, with no previous history of traumatic injuries, who was examined following several weeks with clinical signs and symptoms of paraesthesia in the lower limbs. Thoracic magnetic resonance imaging revealed the existence of a lytic lesion with clearly defined edges and marginal sclerosis in T4, in addition to involvement of the posterior vertebral elements and compression of the underlying spinal cord. The whole lesion was removed surgically, and the sensitive clinical symptoms disappeared after the procedure. The definite pathological diagnosis was spinal aneurysmal bone cyst.

CONCLUSION

Despite their low incidence, aneurysmal bone cysts of the spine must be taken into account in the differential diagnosis of spinal bone tumours as a possible cause of subacute or chronic compressive myelopathy. Full surgical removal of the tumour is considered the preferred treatment, which is often curative and is associated with a good prognosis of the patient in the long term.

[Differential contribution of preoperatory studies to diagnosis in temporal lobe epilepsy surgery]

INTRODUCTION

It is necessary to know the degree of concordance of preoperative studies in temporal lobe epilepsy (TLE). AIM. To analyze the relative importance of different preoperative tests (vEEG, EEG, SPECT and MRI), the degree of agreement between them, and to develop a Bayesian probability model for diagnosis.

PATIENTS AND METHODS

We analyzed 73 patients operated by TLE, with a minimum postoperative follow-up of two years. To analyze the localization capability of different test, we used only patients with an Engel's grade I outcome during all the follow-up time (n = 60).

RESULTS

Engel's grades percentages at 2 years were 87.7/8.2/3.0/0.0 (I/II/III/IV, respectively). The preoperative correlation was < 50% for three tests and 33% for the four. MRI studies were found normal in 33.3% of cases. According to the localization index, the arrange was vEEG > RM > SPECT > EEG. The conditional probability of correct localization for a test was vEEG (0.950) > EEG (0.719) > SPECT (0.717) > RM (0.683). Concordance for more than two tests, was = 0.587 (vEEG + MRI). The probability of obtaining a priori correct localization was vEEG (0.983) > RM (0.414) > EEG (0.285) > SPECT (0.209). The Bayesian model is highly reliable.

CONCLUSIONS

Probably it is not always possible to obtain a high degree of agreement among preoperative test, despite this, it is possible to obtain a good functional result. The most effective test is the vEEG.

[Cavernous haemangioma of the skull]

INTRODUCTION

Cavernous haemangiomas are benign tumours that rarely affect the skull. A correct suspicion diagnosis is seldom obtained when typical radiological signs are lacking. In this way a definite diagnosis is only obtained after a surgical procedure in most cases.

CASE REPORT

A 52-year-old female presented a painless, slow-growing tumoration in her right forehead. Skull CT showed an osteolytic lesion located within the right frontal bone. On suspicion of a metastatic origin of the lesion, a systemic research for a primary tumour was performed without significative findings. Finally, en bloc resection of the lesion was performed followed by cranioplasty. Microscopically, the lesion proved to be a cavernous haemangioma of the frontal bone.

CONCLUSION

Despite their low frequency, cavernous haemangiomas must be included in the differential diagnosis of slow-growing osteolytic lesions located within the skull. The elective treatment of this tumours includes a complete resection by craniectomy, with safe bony margins.

[Cystic hemangioblastoma of the junction of the medulla and upper spinal cord associated to von Hippel-Lindau disease. Two case reports and a review of the literature]

INTRODUCTION

Hemangioblastomas are very highly vascularised benign tumours that can present either sporadically or in association with von Hippel-Lindau syndrome in 20% of cases. Only 5-20% of hemangioblastomas are located in the brainstem, and those that occur at the junction of the medulla and upper spinal cord are the ones that are less commonly diagnosed.

CASE REPORTS

Two young patients were diagnosed with von Hippel-Lindau disease after beginning with a cystic hemangioblastoma at the junction of the medulla and upper spinal cord as the first pathological manifestation. Both of them underwent a suboccipital craniotomy and the two lesions were completely removed without any kind of post-operative neurological deficits. One of the patients required a reintervention some years later due to a new recurrence of a symptomatic hemangioblastoma in the dorsal medulla. The genetic study conducted in both patients confirmed the presence of a mutation in the VHL gene, which is responsible for the syndrome they were suffering from.

CONCLUSIONS

The presence of cystic hemangioblastomas of the junction of the medulla and upper spinal cord associated to von Hippel-Lindau disease is very rare. Despite the technical difficulties involved in removing them, the incorporation of the latest neuroimaging and microsurgery techniques has made it possible to significantly reduce the morbidity and mortality rate associated to the surgical treatment of such patients.