Giulio Bertani

Quantitative assessments of traumatic axonal injury in human brain: concordance of microdialysis and advanced MRI

Axonal injury is a major contributor to adverse outcomes following brain trauma. However, the extent of axonal injury cannot currently be assessed reliably in living humans. Here, we used two experimental methods with distinct noise sources and limitations in the same cohort of 15 patients with severe traumatic brain injury to assess axonal injury. One hundred kilodalton cut-off microdialysis catheters were implanted at a median time of 17 h (13-29 h) after injury in normal appearing (on computed tomography scan) frontal white matter in all patients, and samples were collected for at least 72 h. Multiple analytes, such as the metabolic markers glucose, lactate, pyruvate, glutamate and tau and amyloid-β proteins, were measured every 1-2 h in the microdialysis samples. Diffusion tensor magnetic resonance imaging scans at 3 T were performed 2-9 weeks after injury in 11 patients. Stability of diffusion tensor imaging findings was verified by repeat scans 1-3 years later in seven patients. An additional four patients were scanned only at 1-3 years after injury. Imaging abnormalities were assessed based on comparisons with five healthy control subjects for each patient, matched by age and sex (32 controls in total). No safety concerns arose during either microdialysis or scanning. We found that acute microdialysis measurements of the axonal cytoskeletal protein tau in the brain extracellular space correlated well with diffusion tensor magnetic resonance imaging-based measurements of reduced brain white matter integrity in the 1-cm radius white matter-masked region near the microdialysis catheter insertion sites. Specifically, we found a significant inverse correlation between microdialysis measured levels of tau 13-36 h after injury and anisotropy reductions in comparison with healthy controls (Spearmans r = -0.64, P = 0.006). Anisotropy reductions near microdialysis catheter insertion sites were highly correlated with reductions in multiple additional white matter regions. We interpret this result to mean that both microdialysis and diffusion tensor magnetic resonance imaging accurately reflect the same pathophysiological process: traumatic axonal injury. This cross-validation increases confidence in both methods for the clinical assessment of axonal injury. However, neither microdialysis nor diffusion tensor magnetic resonance imaging have been validated versus post-mortem histology in humans. Furthermore, future work will be required to determine the prognostic significance of these assessments of traumatic axonal injury when combined with other clinical and radiological measures.

Rethinking Neuroprotection in Severe Traumatic Brain Injury: Toward Bedside Neuroprotection

Neuroprotection after traumatic brain injury (TBI) is an important goal pursued strenuously in the last 30 years. The acute cerebral injury triggers a cascade of biochemical events that may worsen the integrity, function, and connectivity of the brain cells and decrease the chance of functional recovery. A number of molecules acting against this deleterious cascade have been tested in the experimental setting, often with preliminary encouraging results. Unfortunately, clinical trials using those candidate neuroprotectants molecules have consistently produced disappointing results, highlighting the necessity of improving the research standards. Despite repeated failures in pharmacological neuroprotection, TBI treatment in neurointensive care units has achieved outcome improvement. It is likely that intensive treatment has contributed to this progress offering a different kind of neuroprotection, based on a careful prevention and limitations of intracranial and systemic threats. The natural course of acute brain damage, in fact, is often complicated by additional adverse events, like the development of intracranial hypertension, brain hypoxia, or hypoperfusion. All these events may lead to additional brain damage and worsen outcome. An approach designed for early identification and prompt correction of insults may, therefore, limit brain damage and improve results.

Microscopic versus endoscopic transsphenoidal surgery for pituitary adenoma: Analysis of surgical safety in 221 consecutive patients

• Arachnoid cyst of the fallopian canal should be suspected and sought in all cases of CSF leak or bacterial meningitis (especially Streptococcus pneumonia, Haemophilus influenzae) in overweight middleaged women without any osteo-meningeal breach identified on the tegmen tympani. • A combination of CT scan and MRI allows the diagnosis of arachnoid cyst of the fallopian canal, can be used to rule out other confounding diagnoses and provides all essential preoperative information. • No systematic surgery is needed for arachnoid cysts of the fallopian canal that have no CSF leak. • When a leak from an arachnoid cyst is identified or when it is associated with a history of meningitis, surgery is needed; a middle ear approach allows minimal invasion with good long-term results. • The idiopathic intracranial hypertension syndrome should be sought in cases of arachnoid cyst of the fallopian canal by performing ophthalmological examination and cerebral MRI. References

Role of Intraoperative Neurophysiologic Monitoring in the Resection of Thalamic Astrocytomas

BACKGROUND The thalamus is a deep-seated and crucial structure for the sensorimotor system. It has been long considered a surgically inaccessible area because of the morbidity associated with surgical resections. Astrocytomas of the thalamus are usually treated with bioptic procedures followed by adjuvant treatments. Intraoperative neurophysiologic monitoring (IONM) allows safe and satisfactory resections of lobar gliomas, but few data are available for thalamic lesions. The aim of this study was to review the outcome of a small series of patients with thalamic astrocytomas that were treated with surgical resection with the aid of IONM. METHODS Surgical resection with IONM was performed in 5 patients with thalamic astrocytomas (1 grade I, 1 grade II, 2 grade III, 1 grade IV). Two astrocytomas were in the dominant hemisphere. Preoperative and postoperative neuropsychological assessments were performed in 3 patients. IONM was tailored to the individual patient and consisted of transcranial motor evoked potential monitoring, cortical motor evoked potential monitoring, somatosensory evoked potential monitoring, direct electrical stimulation, electroencephalography, and electrocorticography. RESULTS None of the patients experienced permanent motor deficits; 2 patients had a transient hemiparesis requiring rehabilitation; 1 patient had a transient aphasia, and 1 patient had permanent aphasia. None of the patients had intraoperative seizures, but 1 patient experienced postoperative transient status epilepticus. The extent of resection on postoperative volumetric magnetic resonance imaging was >70% in all cases. CONCLUSIONS Surgical resection of thalamic astrocytomas appeared to be effective and relatively safe when guided by IONM. Larger series of patients are required to confirm these preliminary data.

Is Complex Sphenoidal Sinus Anatomy a Contraindication to a Transsphenoidal Approach for Resection of Sellar Lesions? Case Series and Review of the Literature

BACKGROUND The transsphenoidal approach is considered the gold standard for resection of pituitary adenomas and other sellar region lesions. This approach is guided by a few fundamental anatomic landmarks that conduct the surgeon toward the sellar floor. Some anatomic structures may vary a lot (e.g., intrasphenoidal septa, intercarotid distance) and may be difficult to identify. Pneumatization and conformation of the sphenoidal sinus (SS) plays a key role in accessing the floor of the sella and other skull base structures. A poorly pneumatized SS may be a relative contraindication to the transsphenoidal approach. We analyzed outcome and complications in transsphenoidal surgery for sellar lesions with a difficult SS. METHODS We analyzed 243 consecutive patients who underwent a transsphenoidal approach for sellar lesions. Patients with poor pneumatization of the SS were included. Neurosurgical and endocrinologic outcomes were reported. RESULTS Successful treatment using a transsphenoidal approach with neuronavigation and Doppler ultrasound was achieved in 15 patients with a low degree of pneumatization of the SS. A pituitary adenoma was present in 13 of 15 patients. Endocrinologic and neurosurgical outcomes were similar to patients with normal pneumatization of the SS, showing a cure of disease in 6 of 9 patients with functioning adenomas and an improvement of symptoms in cases of nonfunctioning adenomas. CONCLUSIONS Patients with a poorly pneumatized SS can be treated safely with a transsphenoidal approach using image guidance techniques to avoid major neurovascular complications.

Optic Radiation Diffusion Tensor Imaging Tractography: An Alternative and Simple Technique for the Accurate Detection of Meyer's Loop

BACKGROUND The optic radiation (OR) is a white matter bundle with a very complex anatomy. Its anterior component bends sharply around the tip of the temporal horn, forming the Meyers loop (ML), the sparing of which during surgery is crucial to preserve visual function. Defining its exact anatomy and accurately identifying its position remain challenging, even with diffusion tensor imaging (DTI) tractography and the most refined tracking procedure. We have developed an alternative tracking technique to detect the ML position. METHODS We performed DTI studies in 26 patients undergoing resection of a temporo-parieto-occipital lesion. We then reconstructed the ORs of each patient using 2 techniques (the first developed by our team, the other taken from the literature), using the same tracking software and parameters. We evaluated the accuracy of each technique measuring 3 distances that define the ML position. We created 5 data groups and compared the 2 techniques. Finally, we compared our results with the results from 8 anatomic dissection studies and other tractographic studies. RESULTS Our findings show that our technique allows a more accurate definition of the ML position. We found a statistically significant (P < 0.05) difference for all the distances between the 2 techniques; our results resemble those obtained in dissection studies. Our technique is also easy to perform and repeatable. CONCLUSIONS Our tracking technique may be of marked interest for the evaluation and anatomic definition of the ML position, particularly for neurosurgeons approaching the anterior temporal region.

Subacute posttraumatic ascending myelopathy (SPAM): A potential complication of subarachnoid shunt for syringomyelia?

Context: Treatment of primary spinal syringomyelia is still controversial. Among others, shunting syrinx fluid to the subarachnoid, peritoneal or pleural space has been utilized with varying success. Shunt obstruction, migration, and infection represent the most common complications of these procedures. Findings: The authors present the case of an 81-year-old woman who developed an unusual neurological deterioration resembling a subacute posttraumatic ascending myelopathy (SPAM) after the insertion of a syringosubarachnoid shunt for the treatment of slow-growing D10 syringomyelia. Conclusion/Clinical Relevance: To date, no cases of SPAM secondary to the insertion of a syringosubarachnoid shunt for the treatment of syringomyelia have been reported. The potential pathogenesis related to this phenomenon is discussed.

Bilateral Parkinsonism: when to image?

A 51-year-old man presented with a 1-year history of gait imbalance and difficulties in the execution of fine movements. On examination, he had hypomimia, bilateral and symmetrical bradykinesia and rigidity (unified Parkinson’s disease rating scale (UPDRS) =17). He had no tremor, impairment of eye movement and cerebellar or pyramidal signs. MR scan of brain found a giant inter-hemispheric arachnoid cyst, exerting a moderate mass effect on the basal ganglia bilaterally (figure …