Thomas Decramer

Posterior quadrant disconnection: a fiber dissection study

BACKGROUND Posterior quadrant disconnection can be highly effective in the surgical treatment of selected cases of refractory epilepsy. The technique aims to deafferent extensive areas of epileptogenic posterior cortex from the rest of the brain by isolating the temporoparietooccipital cortex. OBJECTIVE To describe this procedure and relevant white matter tracts with a specific emphasis on the extent of callosotomy in an anatomic study. METHODS Twenty hemispheres were dissected according to Klinglers fiber dissection technique illustrating the peri-insular (temporal stem, superior longitudinal fasciculus, corona radiata) and mesial disconnection (mesiotemporal cortex, cingulum, and corpus callosum). RESULTS Extensive white matter tract disconnection is obtained after posterior quadrant disconnection. Callosal fibers connecting the anterior most part of the parietal cortex invariably ran through the isthmus of the corpus callosum and need to be disconnected, while frontal lobe connections including the corticospinal tract and the anterior two-thirds of the corpus callosum are spared during the procedure. CONCLUSION Our findings suggest the involvement of both the splenium and the isthmus in interhemispheric propagation in posterior cortex epilepsies. Sectioning the total extent of the posterior one-third of the corpus callosum might therefore be necessary to achieve optimal outcomes in posterior quadrant epilepsy surgery.

Stereopsis after anterior temporal lobectomy.

Brain areas critical for stereopsis have been investigated in non-human primates but are largely unknown in the human brain. Microelectrode recordings and functional MRI (fMRI) studies in monkeys have shown that in monkeys the inferior temporal cortex is critically involved in 3D shape categorization. Furthermore, some human fMRI studies similarly suggest an involvement of visual areas in the temporal lobe in depth perception. We aimed to investigate the role of the human anterior temporal neocortex in stereopsis by assessing stereoscopic depth perception before and after anterior temporal lobectomy. Eighteen epilepsy surgery patients were tested, pre- and postoperatively, in 3 different depth discrimination tasks. Sensitivity for local and global disparity was tested in a near-far discrimination task and sensitivity for 3D curvature was assessed in a convex-concave discrimination task, where 3D shapes were presented at different positions in depth. We found no evidence that temporal lobe epilepsy surgery has a significant effect on stereopsis. In contrast with earlier findings, we conclude that local as well as global stereopsis is maintained after unilateral resection of the temporal pole in epilepsy surgery patients. Our findings, together with previous studies, suggest that in humans more posterior visual regions underlie depth perception.

Case report: Superficial siderosis after brachial plexus avulsion

Superficial siderosis is a slow but progressive neurodegeneraive disease caused by a chronic bleed in the subarachnoid space, esulting in hemosiderin deposition alongside the central nerous system [1]. Bilateral sensorineural hearing loss, ataxia and yramidal signs are the most common symptoms, the diagnosis s confirmed by MRI showing hemosiderin deposition as a dark ypointense layer on T2 and gradient-echo sequences. Superficial siderosis is rare with currently no medical treatment vailable. Surgery has been proposed to stop disease progression, f the bleeding source can be identified. In this report we illustrate nd discuss the association between brachial plexus injury and the evelopment of superficial siderosis and stress the importance of arly diagnosis and surgical referral. Is is important to distinguish this case with global superficial iderosis from localized cortical superficial siderosis which is more revelant and is emerging as a key feature of cerebral amyloid ngiopathy [2].

Facing the hidden wall in mesial extratemporal lobe epilepsy

Refractory extratemporal lobe epilepsy (ETLE) tends to have a less favourable surgical outcome in comparison to temporal lobe epilepsy. ETLE poses specific diagnostic and therapeutic challenges, particularly in cases where seizures develop from the midline. This review focuses on the diagnostic challenges and therapeutic strategies in mesial ETLE. The great diversity of interhemispheric functional areas and extensive connectivity to extramesial structures results in very heterogeneous seizure semiology. Specific signs, such as ictal body turning, can suggest a mesial onset. The hidden cortex of the mesial wall furthermore gives rise to specific diagnostic difficulties due to the low localizing value of scalp EEG. Advanced imaging, as well as targeted intracranial studies, can substantially contribute to depict the seizure onset zone since electroclinical findings are difficult to interpret in most cases. Surgical accessibility of the interhemispheric space can be challenging, both for the placement of subdural grids, as well as for resective surgery. When facing the hidden cortex on the mesial wall of the hemispheres, targeted intra- or extra-operative intracranial recordings can lead to satisfactory outcomes in properly selected cases.

White matter tract anatomy in the rhesus monkey: a fiber dissection study

Brain connectivity in non-human primates (NHPs) has been mainly investigated using tracer techniques and functional connectivity studies. Data on structural connections are scarce and come from diffusion tensor imaging (DTI), since gross anatomical white matter dissection studies in the NHP are lacking. The current study aims to illustrate the course and topography of the major white matter tracts in the macaque using Klingler’s fiber dissection. 10 hemispheres obtained from 5 primate brains (Macaca mulatta) were studied according to Klingler’s fiber dissection technique. Dissection was performed in a stepwise mesial and lateral fashion exposing the course and topography of the major white matter bundles. Major white matter tracts in the NHP include the corona radiata, tracts of the sagittal stratum, the uncinate fasciculus, the cingulum and the fornix. Callosal fiber topography was homologous to the human brain with leg motor fibers running in the posterior half of the corpus callosum. The relative size of the anterior commissure was larger in the NHP. NHPs and humans share striking homologies with regard to the course and topography of the major white matter tracts.

A small leak will sink the brain: targeted C1-C2 patching.

BACKGROUND Spontaneous intracranial hypotension syndrome results from spontaneous spinal cerebrospinal fluid (CSF) leaks. The first treatment of choice consists of lumbar epidural blood patching. If this fails, further imaging is mandatory to explore the possibility of targeted therapy. CASE DESCRIPTION We describe a case of a 50-year-old woman who developed spontaneous intracranial hypotension after minor blunt cervical trauma, complicated with bilateral subdural hematomas. Two lumbar epidural blood patches were unsuccessful. Magnetic resonance imaging with intrathecal gadolinium revealed a CSF leak at the C1-C2 level. A targeted blood patch via a percutaneous high thoracic epidural approach was performed, and symptoms disappeared in the immediate postoperative period with a regression of the subdural hematomas on subsequent imaging. CONCLUSIONS A targeted epidural blood patch using an epidural catheter represents an elegant approach to a CSF leak at the C1-C2 region and can be successful in treating patients with severe intracranial hypotension syndrome.

Pocket Pain and Neuromodulation: Negligible or Neglected?

Pain encountered at the site of the implantable pulse generator (IPG) after invasive neuromodulation is a well‐known and important complication. The reported incidence of implant site pain is variable, ranging between 0.4 and 35%. Implant site pain has never been systematically studied and no treatment guidelines are available.

The dentato-rubro-olivary pathway revisited : New MR imaging observations regarding hypertrophic olivary degeneration

Hypertrophic olivary degeneration (HOD) following a lesion of the dentato–rubro–olivary pathway (DROP) is a well‐known imaging finding and has extensively been described in the recent literature. We reviewed our patients with HOD as a result of a lesion of the DROP in order to analyze the disruption of the DROP and the resulting HOD in comparison with the literature. We observed unusual imaging findings in four patients. In two patients it concerned new observations related to the timing and imaging appearances of HOD. HOD became only visible 6 years after a lesion in the red nucleus in one patient and a cystic degeneration of the olivary nucleus was seen 3 years after the HOD in a second patient. In two patients we found HOD that could only be explained by the existence of an afferent feedback loop between the dentate nucleus and the inferior olivary nucleus and by the knowledge that these fibers run through the ipsilateral olivary nucleus before ending in the contralateral olivary nucleus. In one of these patients the lesion was located in the inferior cerebellar peduncle. In the other patient the lesion was located on the midline in the medulla oblongata. The imaging findings in these patients reveal new observations in the stages of imaging appearances in HOD and shed light on the forgotten dentato–olivary afferent feedback loop of the DROP. Clin. Anat. 30:543–549, 2017.

Unexpected Symptomatic Catheter Tip Mass in Chronic Intrathecal Opioid Therapy

Dear Editor, We would like to report an unusual symptomatic catheter tip mass in a chronic intrathecal opioid therapy patient. A 53-year old woman was seen at the outpatient clinic reporting numbness in both legs combined with urinary incontinence, which developed over several weeks. Her significant medical history consisted of amputations of both legs after a complicated history of complex regional pain syndrome (CRPS), triggered by a minor ankle injury. Intrathecal opioid therapy was initiated 18 years earlier due to intractable phantom limb and stump pain. The drug reservoir of the programmable infusion pump was filled with a mixture of morphine (10 mg/ml) and clonidine (2.4 mg/ml). Over the last 10 years, the morphine dose ranged between 2.2 and 3.6 mg/day. The clonidine dose ranged between 630 and 780 mcg/day. Magnetic resonance imaging (MRI) of the spine (Figure 1, A-B) showed a contrast-enhancing lesion at the level of the …

A frontal syndrome due to a brainstem lesion.

A 48-year-old man presented with progressive gait instability over a period of several weeks, during which he sustained a right forearm and right patellar fracture. Neurological examination revealed a vertical nystagmus in all gaze directions, severe slurring of speech, left sided hemiataxia and extensor plantar response. Computed tomography (CT) revealed a large inhomogeneous brainstem lesion with some spontaneous hyperdensity (Fig. 1a, axial CT without contrast). Magnetic resonance imaging (MRI) confirmed a large contrast-enhancing lesion in the lower part of the mesencephalon (Fig. 1b–d) and a second smaller lesion in the left cerebellar hemisphere. Combined CT chest/abdomen revealed a large primary lesion in the left lung and a left adrenal metastasis. Based on these findings, a tentative diagnosis of metastatic lung cancer was made which was further investigated by a percutaneous biopsy of the lung lesion confirming the presence of a large-cell adenocarcinoma. Lung cancer is the most common primary tumor (40–50 %) to metastasize to the brain, followed by breast (15–20 %), skin (5–10 %) and gastrointestinal (4–6 %) tumors [1]. Without treatment, the median survival of patients with brain metastasized lung cancer is 4–7 weeks [2]. The prognosis of this particular patient was extremely poor given the delicate brainstem localization. Several days after admission loss of decorum was noticed and episodes of aggression occurred which were difficult to control. Repeated imaging of the brain excluded hemorrhage or hydrocephalus as a potential cause for the clinical deterioration; the brainstem lesion had slightly grown. We hypothesized these psychiatric symptoms to arise as a consequence of the brainstem lesion. Two rare psychiatric conditions are known to be caused by brainstem lesions. One of them is peduncular hallucinosis (PH), a condition in which the patient suffers vivid and colorful visual hallucinations due to a, typically vascular, lesion in the mesencephalon or thalamus [3]. Although behavioral abnormalities can be seen in PH, the presence of hallucinations is a hallmark feature. A second condition is called pseudobulbar affect (PBA), a disinhibition syndrome in which the patient suffers from strong emotional lability with uncontrollable episodes of crying and/or laughing [4]. We believe our patient had a clinically distinct condition. Neurobehavioral effects of brainstem lesions have been reported, mimicking clinical features of frontal lobe pathology [5]. This is likely due to disruption of ascending neurotransmitter pathways projecting to the frontal and limbic cortex. The importance of ascending pathways such as the reticular activating system in modifying alertness is well described. The brainstem, & T. Decramer thomas.decramer@uzleuven.be