Sphenoid SinusitisSphenoid sinusitis is the least common sinus condition (only 3% of sinusitis cases). The sphenoid sinus is at the very back part of the nose and sits just beneath the base of the brain (neurosurgeons will often go through the sphenoid sinus to get easier access the brain for pituitary gland operations called trans-sphenoidal hypophysectomy). The big problem with sphenoid sinusitis is that infection of the sinus may cause a bad, dull, non-descript, vague headache that will not go away. The difficulty in making the diagnosis is that it is not considered as classic sinus symptoms such as a runny nose are often not there. A CT scan of the paranasal sinuses can tell if significant sphenoid sinus infection is present. The headache may be made worse by changes in posture, walking, stooping down or prolonged standing. Fever is usually absent. The location of the headache can be almost anywhere. The nerve supplying sensation from the sphenoid sinus is the posterior ethmoid branch of the ophthalmic division of trigeminal nerve. This could result in pain being felt in the eye, or forehead. Some people will have pain in the back of the head, or pain on top of the head. No single pain location is diagnostic. The pain in these cases can disrupt sleep. (Remember that hypnic headache is also a cause of headache that disrupts sleep). In my own practice, I have probably seen only 2 cases that would meet this criteria in the last 4-5 years. One had facial pain, the other had pain in the top of the head. In Northern Ireland, where I practice, 20-25% of all people referred to me have a headache disorder. I estimate that chronic infection of the sphenoid sinus causing chronic daily headache must either be rare or frequently overlooked. If published cases of sphenoid sinusitis are reviewed, headache is the most common feature. One paper reviewed 354 cases of sphenoid sinus problems (not all were sinusitis, some were sphenoid sinus tumors). About 200 of these 354 cases had isolated sphenoid sinusitis. Of those 200 cases with isolated sphenoid sinusitis, 87% had headache as a symptom. Diplopia or numbness of the face was a lot less common in sinusitis than in tumor cases. Blurred vision can also occur, as the main nerve from the eye - the optic nerve, passes very close to the upper outer boundary of the sphenoid sinus. In about 4% of people there is no bony covering at the back of the sphenoid sinus, just a tough membrane, making the brain and nerves there more vulnerable. Sphenoid sinus infection should always be considered when trying to determine the cause of meningitis.
Cranial Nerve Involvement
In isolated chronic infection of the sphenoid sinus, cranial nerve involvement is rare. If cranial nerves become involved, it is much easier to make a diagnosis. The most common nerve involved is the abducens - causes double vision on looking to the side where the abducens is affected. The optic nerve can be involved causing blurred vision. In severe cases of sphenoid sius infection a cavernous sinus syndrome or even cavernous sinus thrombosis can occur. This is not usually the case in isolated sphenoid sinusitis - the usually problem would appear to be persistent, severe headache. (Diagram of right sphenoid sinus, Courtesy of Bartleby.com creative commons license). Diagnosis of Sphenoid SinusitisIf you are not aware of this condition, or don't consider it, you are unlikely to make it.On a CT Scan of Brain or MRI Brain Scan, sinus inflammation is extremely common, and is often dismissed as irrevelant. It is always worth reviewing CT images in chronic daily headache cases to determine whether the amount of sinus inflammation is severe enough to warrant ENT opinion. If Sphenoid Sinusitis is suspected as a cause of chronic daily headache, then a CT Brain Scan and/or paranasal sinuses CT is probably the best single test. On MRI brain scans, bones do not show up very well, although if there is a suspicion that infection has spread to the brain, an MRI is a very good idea (the Lawson and Reino algorithim is recommended for radiological decision-making). If a CT shows an empty sphenoid sinus, you do not have sphenoid sinus headaches. If there is a small amount of inflammation, it is unlikely that headaches are due to sphenoid infection, or at the very least, surgery to the sphenoid sinuses is going to be an expensive mistake. In my own practice, I would not be expecting an ENT surgeon to operate unless the sphenoid sinus was almost completely full of inflammatory material or was showing signs of erosion towards the brain. The other reason for operation is if there is concern that the lesion in the sphenoid is not infection, but one of the other causes (see list below) Can Isolated Sphenoid Sinusitis be anything else?Here's the different things that can cause or mimic sphenoid sinusitis:
Treatment of Sphenoid SinusitisThe entry to the sinus is via a small hole in the upper middle front wall of the sphenoid sinus called the ostium.If the entry to the ostium is blocked by inflammation of nasal lining (rhinitis), then decongestants and anti-inflammatory nasal spray (like flixotide) may help the sinus to drain. More often, by the time isolated sphenoid sinusitis has been diagnosed, these have been tried on several occasions, and some sort of surgery is likely to be recommended by your ENT surgeon. The usual surgery, in modern practice, is FESS - Functional Endoscopic Sinus Surgery. I am not an ENT specialist, so will not make too much comment. However, you should know that FESS involves passing a fine endoscope up the nose. The surgeon tries to get the fine tube into the sinus to drain it, and take samples for laboratory analysis. Patient satisfaction with FESS is usually high. FESS requires a lot of skill, and when operating on the sphenoid sinus there are several critical structures just through the wall - internal carotid arteries, the cavernous venous sinus, abducens nerve, optic nerve and the pituitary gland.
Sphenoid Sinusitis ReferencesGrillone and Kasznica. Isolated Sphenoid Sinus Disease. Otolaryngol Clin North Am 2004;37:435-51 (Free Abstract only)Lawson and Reino Isolated sphenoid disease. An analysis of 132 cases. Laryngoscope 1997;107:1590-5 (Free Abstract only) Hamid O et al. Anatomic Variations of the Sphenoid Sinus and Their Impact on Trans-sphenoid Pituitary SurgerySkull Base. 2008; 18: 9–15. (Free Full text)
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