RESUMEN
BACKGROUND AND OBJECTIVES: The retrosigmoid approach with transtentorial extension (RTA) allows us to address posterior cranial fossa pathologies that extend through the tentorium into the supratentorial space. Incision of the tentorium cerebelli is challenging, especially for the risk of injury of the cranial nerve (CN) IV. We describe a tentorial incision technique and relevant anatomic landmarks. METHODS: The RTA was performed stepwise on 5 formalin-fixed (10 sides), latex-injected cadaver heads. The porus trigeminus's midpoint, the lateral border of the suprameatal tubercle (SMT)'s base, and cerebellopontine fissure were assessed as anatomic landmarks for the CN IV tentorial entry point, and relative measurements were collected. A clinical case was presented. RESULTS: The tentorial opening was described in 4 different incisions. The first is curved and starts in the posterior aspect of the tentorium. It has 2 limbs: a medial one directed toward the tentorium's free edge and a lateral one that extends toward the superior petrosal sinus (SPS). The second incision turns inferiorly, medially, and parallel to the SPS down to the SMT. At that level, the second incision turns perpendicular toward the tentorium's free edge and ends 1 cm from it. The third incision proceeds posteriorly, parallel to the free edge. At the cerebellopontine fissure, the incision can turn toward and cut the tentorium-free edge (fourth incision). On average, the CN IV tentorial entry point was 12.7 mm anterior to the SMT base's lateral border and 20.2 mm anterior to the cerebellopontine fissure. It was located approximately in the same coronal plane as the porus trigeminus's midpoint, on average 1.9 mm anterior. CONCLUSION: The SMT and the cerebellopontine fissure are consistently located posterior to the CN IV tentorial entry point. They can be used as surgical landmarks for RTA, reducing the risk of injury to the CN IV.
Asunto(s)
Procedimientos Neuroquirúrgicos , Humanos , Procedimientos Neuroquirúrgicos/métodos , Fosa Craneal Posterior/cirugía , Fosa Craneal Posterior/anatomía & histología , Cadáver , Traumatismos del Nervio Craneal/prevención & control , Traumatismos del Nervio Craneal/etiología , Craneotomía/métodos , Masculino , Nervio Troclear/anatomía & histología , Nervio Troclear/cirugíaRESUMEN
OBJECTIVES: Several factors contribute to the anatomical complexity of the trochlear nerve, including small diameter, complex and longest intracranial course, deep location, and numerous neurovascular relationships. A 3-dimensional (3D) photorealistic model of the cranial nerves provides a detailed and immersive representation of the anatomy, enabling one to improve surgical planning, advanced surgical research, and training. The purpose of this work is to present a 3D photogrammetric study for a more intuitive and interactive way to explore and describe the entire course of trochlear nerve. METHODS: Two injected-fixed head human specimens (4 sides) were examined. The dissection protocol was divided into the following steps: 1) brain hemisphere exposure; 2) hemispherectomy dissecting all cranial nerves and partial removal of the free edge of the tentorium; 3) middle fossa and lateral wall of cavernous sinus exposure; and 4) orbital exposure. A detailed 3D photogrammetric model was generated for each dissection step. RESULTS: Four main volumetric models were generated during a step-by-step layered dissection of the entire nerve pathway highlighting its different segments. Finally, a full and integrated model of the entire course of the nerve was created. The models are available for visualization on monoscopic display, virtual, and augmented reality environment. CONCLUSIONS: The present photogrammetric model provides a more comprehensive understanding of the nerve's anatomy in its different segments, allows for customizable views thus simulating different perspectives, and can be a valuable alternative to traditional dissections. It is an advanced tool for surgical planning and surgical simulation as well as virtual reality representation of the anatomy.
Asunto(s)
Imagenología Tridimensional , Modelos Anatómicos , Fotogrametría , Nervio Troclear , Humanos , Nervio Troclear/anatomía & histología , Nervio Troclear/cirugía , Imagenología Tridimensional/métodos , Fotogrametría/métodos , Disección/métodos , CadáverRESUMEN
TITLE: Parálisis central del nervio troclear tratada con debilitamiento del músculo oblicuo inferior.
Asunto(s)
Músculos Oculomotores , Enfermedades del Nervio Troclear , Humanos , Músculos Oculomotores/inervación , Movimientos Oculares , Estudios Retrospectivos , Nervio TroclearRESUMEN
We present the case of a 17-year-old male, who complained of a 1-year onset of pulsatile headache, dysphagia, speech changes, and emotional lability. Neuroimaging revealed a large left-sided contrast-enhancing tumor located at the infratentorial space consistent with a large trochlear nerve schwannoma. The tumor was compressing the brainstem, obstructing the outflow of the third and lateral ventricles causing hydrocephalus, and disturbing the cortico-bulbar pathways bilaterally leading to the diagnosis of pseudobulbar palsy. After the patient consented the surgical procedure, he was operated through a subtemporal transtentorial approach placed in the lateral position. A lumbar drain was used for brain relaxation during the procedure and image guidance to define the limits of surgical exposure. A microsurgical technique was used, aiming to preserve the cranial nerves and the vascular structures running through the perimesencephalic cisterns. Gross total resection was achieved and clinical course remained uneventful aside from a transient third nerve palsy. Symptoms improved and the three-month follow-up revealed an almost complete function of the oculomotor nerve (Video 1). Trochlear nerve schwannomas are the rarest variety of the cranial nerve schwannomas. Depending on tumor size, clinical and neuroimaging signs of mass effect and brainstem compression, treatment can be observation, microsurgical resection through cranial base approaches or radiosurgery.1-5.
Asunto(s)
Neoplasias de los Nervios Craneales , Hidrocefalia , Neurilemoma , Enfermedades del Nervio Troclear , Masculino , Humanos , Adolescente , Nervio Troclear/cirugía , Enfermedades del Nervio Troclear/diagnóstico por imagen , Enfermedades del Nervio Troclear/cirugía , Enfermedades del Nervio Troclear/patología , Procedimientos Neuroquirúrgicos/métodos , Neoplasias de los Nervios Craneales/diagnóstico por imagen , Neoplasias de los Nervios Craneales/cirugía , Neurilemoma/diagnóstico por imagen , Neurilemoma/cirugía , Hidrocefalia/cirugíaRESUMEN
OBJECTIVES: To evaluate the effect of inferior oblique (IO) myectomy on ocular torsion according to the absence of the trochlear nerve in unilateral congenital superior oblique palsy (UCSOP). METHODS: We retrospectively reviewed the clinical data of patients who had been diagnosed with UCSOP and underwent ipsilateral IO myectomy (n = 43). Patients were classified into the present and absent groups according to the absence of the trochlear nerve and superior oblique hypoplasia on magnetic resonance imaging (MRI). For quantitative analysis of ocular torsion, disc-fovea angles (DFA) were collected in both eyes using fundus photographs taken within three months before surgery and one month after surgery. RESULTS: DFA of the paretic eye did not differ according to the absence of the trochlear nerve (9.4±5.6° in the present group vs. 11.0±5.4° in the absent group, p = 0.508). However, the present group had a larger DFA in the non-paretic eye than the absent group (14.1±6.7° in the present group vs. 8.0±5.0° in the absent group, p = 0.003). The change of ocular torsion after IO myectomy in the paretic eye was -5.3±3.7° in the present group and -4.8±3.5° in the absent group, respectively (p = 0.801). In the non-paretic eye, the change in DFA was -1.5±3.0° in the present group, which was larger than that in the absent group (0.7±2.6°, p = 0.047). In the multivariate analysis, the change in DFA was correlated with only the preoperative DFA (standardized ß = -0.617, p<0.001 in the paretic eye, and standardized ß = -0.517, p<0.001 in the non-paretic eye). CONCLUSIONS: In the paretic eye, there was no significant difference in the change of ocular torsion between both groups, whereas in the non-paretic eye, the present group had a larger change in DFA after IO myectomy than the absent group. However, in the multivariable analysis, the change in ocular torsion was significantly correlated with preoperative excyclotorsion but not with the presence of the trochlear nerve itself.
Asunto(s)
Estrabismo , Enfermedades del Nervio Troclear , Humanos , Nervio Troclear/cirugía , Nervio Troclear/anomalías , Nervio Troclear/patología , Enfermedades del Nervio Troclear/cirugía , Enfermedades del Nervio Troclear/congénito , Enfermedades del Nervio Troclear/diagnóstico , Estudios Retrospectivos , Músculos Oculomotores/patología , Fóvea Central , Parálisis/patología , Estrabismo/cirugía , Estrabismo/patologíaRESUMEN
BACKGROUND AND PURPOSE: The trochlear nerve has traditionally been difficult to identify on MR imaging. The advent of 7T MR imaging promises to greatly benefit visualization of small structures due to gains in the signal-to-noise ratio allowing improved spatial resolution. We investigated the utility of a clinically feasible ultra-high-resolution 7T MR imaging protocol for identification of the trochlear nerve, as well as assessment of normal trochlear nerve anatomy. MATERIALS AND METHODS: Coronal high-resolution 2D T2-weighted TSE images used in a 7T epilepsy protocol of 50 subjects at our institution were reviewed by 2 independent radiologists for visualization of the trochlear nerve at the nerve origin and cisternal, tentorial, and cavernous segments. The frequency of nerve visibility within these segments and their anatomy were documented, and disagreements were resolved by joint review. RESULTS: Of the 100 nerves reviewed in 50 subjects, at least 2 segments of the trochlear nerve from the brainstem to the cavernous sinus were identified in 100% of cases. The origins from the brainstem and cisternal segment were visible in 65% and 93% of nerves, respectively. The trochlear nerve was identified at the trochlear groove in 100% of cases and in the posterior wall of the cavernous sinus in 74% of cases. CONCLUSIONS: Coronal high-resolution 2D TSE at 7T reliably identified the trochlear nerve throughout its course and is a promising tool for imaging patients with suspected trochlear nerve pathology.
Asunto(s)
Imagen por Resonancia Magnética , Nervio Troclear , Humanos , Nervio Troclear/diagnóstico por imagen , Nervio Troclear/anatomía & histología , Imagen por Resonancia Magnética/métodos , Tronco EncefálicoRESUMEN
The negative effect of hypogravity on the human organism is manifested to a greater extent after the astronauts return to the conditions of habitual gravity. In this work, to elucidate the causes underlying atypical nystagmus, arising after the flight, we studied structural changes in the motoneurons of the trochlear nerve after a 7-day readaptation of mice to the conditions of Earth's gravity. It is known, that motoneurons of the trochlear nerve innervate the muscle that controls the movement of the eyes in the vertical direction. We showed that the number of axodendritic synapses and some other morphological parameters of motoneurons changed by microgravity can return to their original state in 7 days. However, according to some parameters, motoneurons retain a "memory" of the action of microgravity and do not completely restore the structure. The volume of the soma, the shape of the nuclei, the number and orientation of dendrites do not return to pre-flight parameters. The number of dendrites after 7 days of adaptation remained increased, and the proportion of dendrites in the ventrolateral direction became 2.5 times greater than in motoneurons after space flight. The increased number of mitochondria after space flight became even more significant after readaptation. Microgravity-induced plastic changes retain to some extent "memory traces" after readaptation to Earth's gravity. It can be assumed that the restoration of the function of the trochlear nuclei (overcoming nystagmus) is carried out not only by reversible restoration of the structure of neurons, but partially using those mechanisms that are formed in weightlessness.
Asunto(s)
Vuelo Espacial , Ingravidez , Animales , Astronautas , Humanos , Ratones , Plásticos , Nervio Troclear , Ingravidez/efectos adversosRESUMEN
Background and purpose: This study analyzed the relationship of trochlear nerve with neurovascular structures using craniometric measurements. The study was aimed to understand the course of trochlear nerve and minimize the risk of injury during surgical procedures. Methods: Twenty trochlear nerves of 10 fresh cadavers were studied bilaterally using endoscopic assistance through the view afforded by the lateral infratentorial-supracerebellar, and the combined presigmoid-subtemporal transtentorial approaches. Trochlear nerves were exposed bilaterally taking seven parameters into consideration: the distance between the cisternal segment of trochlear nerve and vascular structures (superior cerebellar artery/SCA; posterior cerebral artery/PCA), the origin of the trochlear nerve in the brain stem, the angle in the level of tentorial junction, length, diameter, and length of nerve in the cisternal segment. Results: We identiï¬ed the brain stem and cisternal segments of the trochlear nerve. The lateral infratentorial supracerebellar approach allowed the exposure of the cisternal segments (crural and ambient cisterns), including the origin of the nerve in the brain stem. The combined presigmoid-subtemporal transtentorial approaches provided visualization of the cisternal segment of the nerve and the free edge of the tentorium. In this study, the mean length and width of the trochlear nerve in the cisternal segment were 30.3 and 0.74 mm, respectively. Length of the trochlear nerve from its origin to its dural entrance was 37.2 mm, tentorial dural entrance angle of the trochlear nerve and exit angle of the trochlear nerve from the brain stem were 127.0 degrees and 54 degrees, PCA to trochlear nerve in mid ambient cistern and SCA to trochlear nerve in mid ambient cistern were 7.3 mm and 6.8mm. Conclusion: Trochlear nerve is vulnerable to injury during the surgical procedures. Therefore, it is necessary to have a sufficient knowledge of the anatomy of cisternal segment and its relationship with adjacent neurovascular structures. The anatomical and craniometric data can be helpful in middle and posterior fossa surgery in minimizing the potential injury of the trochlear nerve.
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Tronco Encefálico , Nervio Troclear , Encéfalo , Cadáver , Endoscopios , Humanos , Nervio Troclear/irrigación sanguínea , Nervio Troclear/cirugíaRESUMEN
We present the case report of a patient who presented with intermittent diplopia and left hypertropia associated with an apparent left superior oblique palsy. After dissociation with cover testing, he showed conjugate rhythmic vertical eye movements present in all gazes, thought to represent rapid rhythmically alternating fixation. The vertical rhythmic movement resolved after strabismus surgery.
Asunto(s)
Estrabismo , Enfermedades del Nervio Troclear , Diplopía/diagnóstico , Diplopía/etiología , Movimientos Oculares , Humanos , Masculino , Músculos Oculomotores/inervación , Músculos Oculomotores/cirugía , Estrabismo/complicaciones , Estrabismo/cirugía , Nervio Troclear , Enfermedades del Nervio Troclear/complicaciones , Enfermedades del Nervio Troclear/cirugíaRESUMEN
Cranial nerve schwannomas accounts for around 8% of all benign intracranial tumors, arising most commonly from the vestibular nerve, followed by the trigeminal nerve and other lower cranial nerves. However, trochlear schwannoma in a patient without neurofibromatosis-2 are extremely rare and to date, fewer than 100 cases have been reported in the literature. They are either asymptomatic or present with ophthalmologic or neurologic symptoms. Diplopia is the most common initial symptom. As the tumor grows, it can compress the surrounding brainstem and other cranial nerves, causing neurologic symptoms. Asymptomatic lesions are detected incidentally following imaging for some other reason. There are no clear guidelines for the management of these tumors. In general, small asymptomatic tumors are closely observed by serial imaging and symptomatic or larger tumors are managed by surgical excision and/or stereotactic radiosurgery.1-7 Here we present a 41-year-old female patient with incidentally detected left trochlear schwannoma during the follow-up magnetic resonance imaging (MRI) scans. She was followed up regularly with multiple repeat MRI. Recently she started complaining of occasional headaches, and MRI showed a left peimesencephalic cistern tumor causing mass effect on the ipsilateral midbrain. There was also significant brainstem edema. Hence she underwent left retromastoid suboccipital craniectomy, lateral supracerbellar approach, and complete excision of the tumor. Postoperatively the patient had an uneventful recovery without any new neurologic deficits. At 6 months' follow-up the patient is doing well.
Asunto(s)
Neoplasias de los Nervios Craneales , Neurilemoma , Neurofibromatosis 2 , Enfermedades del Nervio Troclear , Adulto , Neoplasias de los Nervios Craneales/diagnóstico por imagen , Neoplasias de los Nervios Craneales/patología , Neoplasias de los Nervios Craneales/cirugía , Femenino , Humanos , Imagen por Resonancia Magnética , Neurilemoma/diagnóstico por imagen , Neurilemoma/cirugía , Nervio Troclear/cirugía , Enfermedades del Nervio Troclear/diagnóstico por imagen , Enfermedades del Nervio Troclear/patología , Enfermedades del Nervio Troclear/cirugíaRESUMEN
BACKGROUND AND OBJECTIVE: Cranial nerve schwannomas almost always arise from sensory or mixed nerves. Motor cranial nerves, such as the trochlear nerve, are rarely associated with schwannomas. No consensus has yet been made for surgical intervention because of the low number of reported cases of trochlear nerve schwannomas. This study comprises a systematic review of the literature and our experience for surgically treated trochlear nerve schwannomas. METHODS: Three databases (Web of Science, PubMed, and Cochrane Library) were searched without date restrictions. Studies were included if they were published in the English literature and presented patients of any age who underwent surgical treatment for trochlear schwannoma. Data extracted from the included studies were combined with our experience. RESULTS: Forty-one studies, presenting 43 patients, met the inclusion criteria. The total number of patients was 45 after our experience was added. The most common symptoms were diplopia (62.2%), headache (46.7%), and motor weakness (37.8%). Mean age during the diagnosis was 45.1 years. Although the subtemporal transtentorial approach (n = 14) is the most preferred method, its application has decreased in recent years. In the last decade, the lateral suboccipital approach (n = 11) has gained popularity. Residual postoperative trochlear nerve deficit was detected in 81% of patients. The probability of neurologic deficit was not statistically associated with tumor volume (P = 0.914), location (P = 0.669), or resection rate (P = 0.554). CONCLUSIONS: Although trochlear schwannomas are rare and their treatment involves challenges, total resection with the proper approach provides the most desirable results.
Asunto(s)
Neoplasias de los Nervios Craneales , Neurilemoma , Enfermedades del Nervio Troclear , Neoplasias de los Nervios Craneales/patología , Diplopía/etiología , Humanos , Persona de Mediana Edad , Neurilemoma/complicaciones , Neurilemoma/diagnóstico por imagen , Neurilemoma/cirugía , Nervio Troclear/cirugía , Enfermedades del Nervio Troclear/patologíaRESUMEN
PURPOSE: To date, no study has explored the root exit zone of the trochlear nerve (TroN) on the dorsal brainstem; therefore, we aimed to characterize the location using magnetic resonance imaging (MRI). METHODS: A total of 85 patients underwent thin-slice axial T2-weighted MRI. RESULTS: TroN was identified in 91% of 85 patients, 60 (71%) on the right side, and 67 (79%) on the left. The distances between the apex of the inferior colliculus and the original site of TroN on the dorsal brainstem were variable, with mean values of 2.4 ± 1.8 mm (range 0-8 mm) on the right and 2.2 ± 1.7 mm (range 0-5 mm) on the left. Most of the root exit zones were distributed within 0-5 mm below the apex of the inferior colliculus. In addition, the distances between the midline and the root exit zones of the TroN were variable, with mean values of 4.4 ± 1.4 mm (range 1.9-7.5 mm) on the right and 4.6 ± 1.6 mm (range 1.1-7.8 mm) on the left. Most of the root exit zones were located within 1-7 mm range lateral to the midline. CONCLUSIONS: The root exit zone of the TroN may be mostly located in a small square area measuring 8 mm × 8 mm, lying at and below the apex of the inferior colliculus. The TroN may arise from any site in the square area, and significant attention is necessary when performing surgical maneuvers in and around it.
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Imagen por Resonancia Magnética , Nervio Troclear , Tronco Encefálico/diagnóstico por imagen , HumanosRESUMEN
BACKGROUND: Ocular motor nerve palsies (OMNP) frequently cause patients to present in an emergency room. In the following study, we report the differential diagnosis of OMNP by use of magnetic resonance imaging (MRI) and CSF examination as a standard. METHOD: We performed a data analysis of N = 502 patients who presented with oculomotor, trochlear, and/or abducens nerve palsy in the emergency room of the Department of Neurology, University of Ulm, between January 2006 and December 2019. We report clinical and MRI scan findings in all patients; furthermore, the CSF of 398 patients has been analysed. RESULTS: Abducens nerve palsies were most common (45%), followed by palsies of the oculomotor (31%) (CNP III) and trochlear nerve (15%). Multiple OMNPs were seen in 9% of our cohort. The most common causes included inflammations (32.7%), space-occupying lesions, such as aneurysms or neoplasms (17.3%), diabetes mellitus (13.3%), and brainstem infarctions (11%). Still 23.4% of the patients could not be assigned to any specific cause after differential diagnostic procedures and were described as idiopathic. One of three patients with an inflammation and 39% of the patients with space-occupying lesions showed additional cranial nerve deficits. CONCLUSION: Inflammation and space-occupying processes were the most frequent causes of OMNP, although brainstem infarctions also play a significant role, in particular in CNP III. The presence of additional CNPs increases the probability of an inflammatory or space-occupying cause.
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Enfermedades del Nervio Abducens , Enfermedades de los Nervios Craneales , Enfermedades del Nervio Oculomotor , Enfermedades del Nervio Troclear , Enfermedades del Nervio Abducens/complicaciones , Enfermedades del Nervio Abducens/etiología , Enfermedades de los Nervios Craneales/complicaciones , Enfermedades de los Nervios Craneales/diagnóstico , Diagnóstico Diferencial , Humanos , Enfermedades del Nervio Oculomotor/diagnóstico , Enfermedades del Nervio Oculomotor/etiología , Parálisis/etiología , Nervio Troclear , Enfermedades del Nervio Troclear/complicaciones , Enfermedades del Nervio Troclear/diagnósticoRESUMEN
ABSTRACT: Neuro-Behçe disease (NBD) has a predilection for affecting the parenchyma of the upper brainstem; however, involvement of the fourth nerve nucleus or fascicle by NBD has not been previously described. We report a case of a young man with acute right fourth nerve palsy and history of Behçet disease with an enhancing lesion in the left caudal midbrain corresponding to the left trochlear nerve nucleus/fascicle. This is the first described case of NBD producing nuclear/fascicular fourth nerve palsy. It also demonstrates an important clinicoanatomical correlate of decussation of fourth nerve fibers to the opposite side after exiting the midbrain.