Session 3: State-of-the-Art: Sphenoid wing meningioma

Meningiomas are the most common primary orbital brain tumour, with 20% centred on the sphenoid wing (SWM). There are two main growth patterns: the nodular or 'en-masse', and the more diffuse 'en-plaque' patterns. They are classified according to their site of origin along the sphenoid ridge: lateral, middle or clinoidal. Hyperostosis and sclerosis are common and are usually due to tumour infiltration rather than a reactive phenomenon.MRI gives excellent contrast and spatial resolution, particularly with intravenous gadolinium. SWM is characterised as a well-circumscribed durally based mass, with variable T1 and T2 signal characteristics. On T2 they are usually iso- to hyperintense, and a dural tail occurs in about three quarters of cases. Up to 50% of tumours have elicited parenchymal vasogenic oedema, although this doesn't correlate with tumour size. Vessels that occur in a meningioma are visualised as serpiginous flow-void structures and can give an indication of tumour vascularity.Diffusion-weighted sequences can be helpful and rely on free random “Brownian” motion of water molecules between the intracellular and extracellular space. In lesions with increased cellularity, such as SWM, that restriction of water molecule motion is depicted as hyperintensity on the diffusion-weighted trace image. This is quantified on the corresponding apparent diffusion coefficient (ADC) map, and gives a measure of cellularity, with restricted diffusion depicted as low signal. It can also help to differentiate between tumour mass and vasogenic oedema in SWM.Meningiomas have a typical spectrum on MR spectroscopy (MRS) with an alanine peak and sometimes a glutamine peak, and although MRS is not routinely used in clinical practice, it may be helpful in atypical meningiomas. Meningiomas also express somatostatin receptors, hence the value of 68-Gallium Dotatate CT/MR imaging: the radio-labelled gallium attaches to the somatostatin receptor thus is avidly taken up thes tumours. This modality is useful where there is uncertainty about the diagnosis, where subtle recurrence is suspected or to clarify whether associated bony changes are reactive or due to infiltration.The differential diagnoses for SWM include metastasis and fibrous dysplasia, amongst other lesions, but CT can differentiate the latter due to the presence of preservation of the cortex and typical regions of intra-diploic “ground-glass” matrix despite the additional bony expansion and sclerosis.

Surgical resection of spheno-orbital meningiomas (SOM) is challenging, requiring a multidisciplinary surgical approach. In Manchester we have a dedicated skull base service with bimonthly MDT clinics involving Neurosurgeons, ENT and Orbital surgeons. We present a difficult case which came through our service of a young female developing sequential spheno-orbital meningiomas requiring surgical intervention.We then present a retrospective analysis of patients with SOM who underwent joint neurosurgical and orbital surgical procedures between January 2000 and June 2017. Twenty four operations were performed. The indication for surgery was evidence of visual dysfunction in 17 (71%), the remaining 7 (29%) had high risk of visual loss clinically or radiologically. Three-months post operatively, vision was stable in 13 (58%), improved in 6 (21%) and worse in 5 (17%). Average long-term follow-up was 82 months (1-220). Fourteen (58%) maintain improved or stable visual function. Four (17%) had reduced vision due to regrowth of the tumour at an average of 24 months.SOMs are very challenging to treat surgically. In our experience they predominantly affect young females with aggressive disease. Visual function can be improved or stabilised in the majority.

Sphenoid wing meningiomas are not curable, which raises the questions of “how to deal with residual disease”, “does partial resection make the tumour more pervasive”, and “how can we reduce or stop the marked periocular oedema due to fluid congestion around the superior orbital fissure (this oedema often being the earliest, and very troublesome, symptom)”?With compressive optic neuropathy due to orbital tissue, one can get an excellent relief of neuropathy using a retrocaruncular medial decompression (complete ethmoidectomy, medial half of floor, and posterior half of infero-medial strut), whereas lateral bone decompression and soft-tissue resection through an extended upper lid skin-crease incision is especially useful where there is a larger hyperostotic component with marked proptosis; all orbital approaches can be combined with neurosurgery where necessary. Radiotherapy does slow the progression of the disease and so is very useful adjunct.Remember to avoid progestogen-containing HRT, as these tumours are known to be driven by them and the medication is often prescribed at the age when the tumours are most common.

There are 2 important and commonly used neurosurgical approaches to the orbit; variations of the pterional oblique lateral craniotomy to the middle and anterior fossae and secondly the supra-orbital craniotomy ideal for reaching the superior contents of the orbit. Both approaches will be described and examples given with both intra and extradural pathologies.

This presentation covers sphenoid wing meningioma from a radiotherapist’s perspective. An example case history of a grade II sphenoid wing meningioma is used to outline the indications for radiotherapy in meningioma and the principles of radiotherapy planning, including the typical radiotherapy doses used for different grades of meningioma and how nearby radiosensitive normal tissues influence the radiotherapy plan. The evidence for the effectiveness of radiotherapy is discussed and the case history concludes by considering the treatment options for recurrent disease, including re-irradiation. Finally, the presentation touches on proton therapy and the need for comparative studies to evaluate its place in the management of meningioma.