Intraoperative Neurophysiologic Monitoring in Predicting Dysphagia After Brainstem and Fourth Ventricle Surgery.

OBJECTIVE: Dysphagia represents the main complication of posterior fossa neurosurgery. Adequate diagnosis of this complication is warranted to prevent untimely extubation with subsequent aspiration. Intraoperative neurophysiologic monitoring (IONM) modalities may be used for this purpose. However, it is not known which IONM modality may be significant for diagnosis. This study aimed to define the most significant IONM modality for dysphagia prognostication after posterior fossa neurosurgery. METHODS: The analysis included 46 patients (34 with tumors of the fourth ventricle and 12 with brainstem localization) who underwent surgical excision of the tumor. Neurologic symptoms before and after neurosurgery were noted and magnetic resonance imaging with the subsequent volume estimation of the removed mass was performed, followed by an IONM findings analysis (mapping of the nucleus of the caudal cranial nerves [CN] and corticobulbar motor-evoked potentials [CoMEP]). RESULTS: Aggravation of dysphagia was noted in 24% of the patients, more often in patients with tumor localization in the fourth ventricle (26%) than in those with brainstem mass lesions (16%). Mapping of the caudal cranial nerve nuclei did not correlate with the dysfunction of these structures. CoMEP was significantly associated with the neurologic state of the CN. The decrease in CoMEP is a significant prognostic factor for postoperative bulbar symptoms appearance or aggravation. CONCLUSIONS: Mapping the CN is an important identification tool. The CoMEP modality should be used intraoperatively to determine the functional state of the CN and predict postoperative dysphagia.

Comparison of Cerebral Autoregulation Above and Below the Tentorium of the Cerebellum In Neurosurgical Patients with Transtentorial ICP Gradient.

INTRODUCTION: Cerebral autoregulation is an essential mechanism for maintaining cerebral blood flow stability. The phenomenon of transtentorial intracranial pressure (ICP) gradient after neurosurgical operations, complicated by edema and intracranial hypertension in the posterior fossa, has been described in clinical practice but is still underinvestigated. The aim of the study was to compare autoregulation coefficients (i.e., pressure reactivity index [PRx]) in two compartments (infratentorial and supratentorial) during the ICP gradient phenomenon. METHODS: Three male patients, aged 24 years, 32 years, and 59 years, respectively, were involved in the study after posterior fossa surgery. Arterial blood pressure and ICP were invasively monitored. Infratentorial ICP was measured in the cerebellar parenchyma. Supratentorial ICP was measured either in the parenchyma of the cerebral hemispheres or through the external ventricular drainage. Cerebral autoregulation was evaluated by the PRx coefficient (ICM + , Cambridge, UK). RESULTS: In all patients, ICP was higher in the posterior fossa, and the transtentorial ICP gradient in each patient was 5 ± 1.6 mm Hg, 8.5 ± 4.4 mm Hg, and 7.7 ± 2.2 mm Hg, respectively. ICP in the infratentorial space was 17 ± 4 mm Hg, 18 ± 4.4 mm Hg, and 20 ± 4 mm Hg, respectively. PRx values in the supratentorial and infratentorial spaces had the smallest difference (- 0.01, 0.02, and 0.01, respectively), and the limits of precision were 0.1, 0.2, and 0.1 in the first, second, and third patients, respectively. The correlation coefficient between the PRx values in the supratentorial and infratentorial spaces for each patient was 0.98, 0.95, and 0.97, respectively. CONCLUSIONS: A high degree of correlation was established between the autoregulation coefficient PRx in two compartments in the presence of transtentorial ICP gradient and persistent intracranial hypertension in the posterior fossa. Cerebral autoregulation, according to the PRx coefficient in both spaces, was similar.

Resection of Pontine Cavernoma with Hemorrhage via Unilateral Uvulotonsillar Keyhole Approach.

The telovelar approach and its modifications are widely used to remove lesions of the fourth ventricle and brainstem. We offer a variant of a unilateral uvulotonsillar approach, which is performed using an open-door keyhole suboccipital craniotomy (Video 1). A 56-year-old woman presented with symptoms of 2 months' duration. Preoperative examination revealed paresis of the left sixth cranial nerve, left seventh nerve paralysis, right-sided hemihypoesthesia, right-sided severe hemiparesis owing to which the patient could not move independently, and dynamic ataxia in the left limbs. Magnetic resonance imaging showed a cavernoma with hemorrhage in the left side of the pons. The surgery was performed in the prone position. After a median skin and soft tissue incision about 6-7 cm long, an open-door keyhole craniotomy was performed. Dura over the left cerebellar hemisphere was opened in a semilunar fashion. The dissection of the uvulotonsillar fissure was performed from its cranial part, where the medial trunk of the cortical segment of the posterior inferior cerebellar artery was the reference point. Following the dissection, the tela choroidea was incised, and the left half of the rhomboid fossa was exposed. After the mapping, the floor of the fourth ventricle was incised in the suprafacial triangle. Cavernoma and hematoma were removed. Hemostasis was achieved. Dura was closed. The attached bone flap was then turned upward and reattached using nonresorbable sutures. Postoperatively, the patient had resolution of sensory and motor disturbances on the right half of the body, and coordination was improved in the left limbs. Postoperative imaging confirmed complete removal of the lesion.

Intra-axial Neurenteric Cyst of Medulla: Case Report and Literature Review.

Neurenteric cysts (NCs) are rare congenital lesions that are thought to result from the persistence of the neurenteric canal connecting primitive gut and neural tube. Despite the congenital nature, NCs can be diagnosed at any age and at a similar frequency in women and men. To our knowledge, 140 intracranial NCs, confirmed by histology, including the patient presented in this review, have been reported since 1952. Parenchymal NCs are extremely rare, and there are no publications describing the intra-axial NCs of the brainstem at the moment. A 19-year-old female presented to the clinic with the following complaints: moderate dysphagia (two to three times per day) for and liquids and solids, dysphonia, vertigo, spontaneous nystagmus, imbalance, and numbness in the left side of the body, including the face. The magnetic resonance imaging (MRI) of the brain showed a well-defined lesion centered in the medulla. The patient underwent a small right-sided keyhole retro-sigmoid craniotomy. Just under the sulcus, a cyst containing pathological amorphous gray-yellow liquid was evacuated. Accessible parts of the capsule were resected without brain injury. Residual particles of the capsule were coagulated. Two months after the operation, the patient presented with similar symptoms. We used the previous craniotomy during the second surgery. After the evacuation of the cyst, a silicone stent was set for connecting with the cerebellopontine cistern and preventing new synechiae formation. As surely as after the first surgery, all neurological symptoms gradually regressed. In two months after surgery, deglutition and sensations recovered, and hemiparesis and imbalance decreased. Postoperative MRI examination two months after surgery showed no evidence of cyst recurrence. Intra-axial NCs are a rare group of congenital pathological lesions with a favorable prognosis. There are no publications of brainstem NCs with intra-axial localization to date. The treatment of choice in this group of patients is complete microsurgical excision followed by long-term observation.