Anatomy of the greater occipital nerve: implications in posterior fossa approaches

PURPOSE

Because of its superficial location in the dorsal regions of the scalp, the greater occipital nerve (GON) can be injured during neurosurgical procedures, resulting in post-operative pain and postural disturbances. The aim of this work is to specify the course of the GON and how its injuries can be avoided while performing posterior fossa approaches.

METHODS

This study was carried out at the department of anatomy at Bordeaux University. 4 specimens were dissected to study the GON course. Posterior fossa approaches (midline suboccipital, paramedian suboccipital, retrosigmoid and petrosal) were performed on 4 other specimens to assess potential risks of GON injuries.

RESULTS

The GON runs around the obliquus capitis inferior (100%), crosses the semispinalis capitis (100%) and the trapezius (75%) or its aponeurosis (25%). Direct GON injuries can be seen in paramedian suboccipital approaches. Stretching of the GON can occur in midline suboccipital and paramedian suboccipital approaches. We found no evidence of direct or indirect GON injury in retrosigmoid or petrosal approaches.

CONCLUSION

Our study provides interesting data regarding the risk GON injury in posterior fossa approaches. Direct GON injuries in paramedian suboccipital approaches can be avoided with careful dissection. Placing retractors in contact with the periosteum and performing a minimal retraction may help to avoid excessive GON stretching in midline suboccipital and paramedian suboccipital approaches. Furthermore, the incision for retrosigmoid approaches should be as lateral as possible and not too caudal. Finally, avoiding extreme patient positioning reduces the risk of GON stretching in all approaches.

Communicating chronic hydrocephalus: A review

Formerly called normal pressure hydrocephalus, communicating chronic hydrocephalus (CCH) is a condition affecting 0.1 to 0.5% of patients over 60years of age. The pathophysiology of this disease is poorly understood, but a defect in cerebrospinal fluid (CSF) resorption appears to be commonly defined as the cause of the neurological disorders. The last important discovery is the description of the glymphatic system and its implication in CCH and CSF resorption. Comorbidities (Alzheimer's disease, microangiopathy, parkinsonism) are very frequent, and involve a diagnostic challenge. The clinical presentation is based on the Hakim and Adams triad, comprising gait disorders, mainly impairing walking, cognitive disorders, affecting executive functions, episodic memory, visuospatial cognition, and sphincter disorders as urinary incontinence (detrusor hyperactivity). The diagnosis is suspected through a set of arguments, combining the clinical presentation, the radiological data of the magnetic resonance imaging (MRI) showing a ventriculomegaly associated with signs of transependymomous resorption of the CSF and disappearance of the cortical sulci, and the clinical response to the depletion of CSF. In the presence of all these elements, or a strong clinical suspicion, the standard treatment will be of a permanent CSF shunt, using a ventriculoatrial or ventriculoperitoneal shunt. The effectiveness of this treatment defines the diagnosis. The clinical improvement is better when treatment occurs early after the onset of the disorders, reaching 75 to 90% of motor improvement.

P09.08 Increased incidence of intracranial meningiomas in patients with acromegaly

BACKGROUND

An increased incidence of various neoplasms has been described in patients with acromegaly and there is evidence to suggest that growth factors are risk factors for the development of meningiomas. We aimed to study if patients with acromegaly are more at risk for developing intracranial meningiomas

MATERIAL AND METHODS

We conducted an observational study on 221 consecutive acromegalic patients recruited between January 1, 2000 and December 31, 2015, and 357 consecutive patients with a non-somatotropic pituitary adenoma recruited between March 1, 2015 and December 31, 2016 in our institution. Patients underwent a gadolinium-enhanced 3D T1 brain MRI to look for meningiomas. The proportion of meningiomas was compared between the two groups and the standardized incidence ratio (SIR) was computed from the incidence rates of meningiomas observed in the population of acromegalic patients and compared to that of the general population given by the local registry of central nervous system tumors.

RESULTS

Patients with acromegaly had a significant risk for developing intracranial meningiomas as compared to patients without acromegaly (7.7% vs. 2.2%, p = .005, OR = 3.45 [1.46; 8.15]). There was a significant increased incidence of intracranial meningiomas in patients with acromegaly (SIR = 126 [25; 367]) as compared to the general population.

CONCLUSION

Our study provides the first evidence that patients with acromegaly are more at risk for developing intracranial meningiomas.

[Intracranial hemorrhage in adults: place of antithrombotic treatment]

BACKGROUND AND PURPOSE

Antithrombotic (anticoagulants and antiplatelets) are responsible for iatrogenic accidents, with a specific impact in neurosurgery. Bleeding complications are the most common and best-known. But the link to antiplatelet or to dual association of antithrombotic treatment with intracranial haemorrhage is not complete yet. We studied the proportion of patients under antithrombotic treatment, when an intracranial hemorrhage occurred, as well as the morbi-mortality of each group of patients (with or without antithrombotic treatment). Finally, we studied the proportion of off-label prescriptions.

METHODS

We conducted a monocentric and comprehensive prospective study on a group of patients. All patients that had been admitted for intracranial hemorrhage to our hospital, in a 5-month period were included in the study.

RESULTS

One hundred and sixty patients admitted for an intracranial hemorrhage were included during 70days of call. Seventy-four of these patients (46.25%) were under antithrombotic treatment: 40 under antiplatelet treatment (54%), 29 under anticoagulant treatment (39.2%), four under dual antithrombotic treatment (5.4%), and one under Arixtra(®). Half of the patients under antithrombotic treatment had poor prognosis as compared to 40% of patients without antithrombotic treatment. Off-label antithrombotic therapy was estimated at 27.3% of all prescriptions.

CONCLUSIONS

The prevalence of antithrombotic therapy in patients is high when intracranial hemorrhage occurs. Some complications could be avoided by decreasing the number of off-label prescriptions and by better controlling their use (using standardized INR). Antiplatelet treatments and new antithrombotic therapies require better drug monitoring which could be part of the establishment of a specific register.

Decompression for Chiari type I-malformation (with or without syringomyelia) by extreme lateral foramen magnum opening and expansile duraplasty with arachnoid preservation: comparison with other technical modalities (Literature review)

Posterior craniocervical decompression is the procedure most currently used for treating Chiari I malformation (alone or in association with syringomyelia in the absence of hydrocephalus). We reviewed the various technical modalities reported in the literature. We present a personal series of 44 patients harboring Chiari type I malformation (CM-I) operated with a suboccipital craniectomy and a C1 (or C1/C2) laminectomy, plus an extreme lateral Foramen Magnum opening, a "Y" shaped dural incision with preservation of the arachnoid membrane, and an expansile duraplasty employing autogenous periosteum. Outcomes were analyzed with follow-up ranging from 1 to 10 years (4 years on average). The presented technique was compared with the other surgical modalities reported in the literature. This comparative study shows that this type of craniocervical decompression achieved the best results with minimal complications and side-effects. Syringomyelia associated with CM-I must be treated by craniocervical decompression alone. Shunting no longer appears to be an appropriate method of treatment for syringomyelia.