Describe lateral sinus thrombophlebitis.

Nature and Presentation

• Lateral (sigmoid) sinus thrombophlebitis is inflammation and thrombosis of the lateral venous sinus secondary to middle ear or mastoid infection.
• It is important because it is a treatable cause of a septicaemic illness that is readily attributed to something else.
• Pathogenesis proceeds in an orderly sequence, and knowing it explains every sign: infection erodes or spreads through the sinus plate → a perisinus abscess forms → the sinus wall becomes inflamed (phlebitis) → a mural thrombus forms on the intima → the thrombus propagates and occludes the lumen → it breaks down and becomes infected, releasing septic emboli into the circulation

Investigation and Treatment

• Blood culture taken during a rigor gives the highest yield.
• Full blood count showing polymorphonuclear leucocytosis and anaemia, which is characteristic of the prolonged septic course
• Contrast-enhanced CT shows the delta (empty triangle) sign — enhancement of the dural wall around a non-enhancing intraluminal clot — and shows the bone and any coexisting abscess
• MR venography (or CT venography) is the investigation of choice, demonstrating absent flow in the sinus and the extent of propagation into the jugular vein and other sinuses
• High-resolution CT of the temporal bone for the ear disease
• Treatment:
• High-dose intravenous antibiotics, broad-spectrum with anaerobic cover, continued for several weeks and guided by culture
• Surgery on the ear — mastoidectomy (canal wall down) to eradicate the disease, with exposure of the sinus plate and removal of the perisinus abscess and granulations until healthy sinus wall is seen on either side
• Whether to open the sinus and evacuate the clot is debated. The modern view is that the sinus need not be opened routinely, since antibiotics and drainage of the perisinus infection suffice; it is reserved for a patient who remains septic despite adequate treatment, when the thrombus is aspirated or the sinus incised and the infected clot removed
• Ligation of the internal jugular vein, once routine, is now rarely performed, and is reserved for continuing septic emboli despite treatment
• Anticoagulation remains controversial — it may limit propagation of thrombus and reduce embolisation, particularly with extension into the cavernous or sagittal sinus, but risks haemorrhage. It is used selectively, and the decision is individualised
• Supportive care — correction of anaemia and dehydration, and nutrition.
• Prognosis is good with prompt treatment; the sinus recanalises in many, and the collateral venous drainage is adequate even if it does not
• Look for coexisting complications — particularly cerebellar abscess and otitic hydrocephalus, both of which are associated with lateral sinus thrombosis and are easily overlooked once the first diagnosis is made
• Take the blood culture during the rigor; bacteraemia is intermittent and this single timing change alters the yield
• The picket-fence pattern matters more than the height of the fever, rising with a rigor and falling by crisis with sweating
• Griesinger sign is oedema behind the mastoid from emissary vein thrombosis, and should be looked for deliberately
• The delta sign on contrast CT shows an enhancing dural wall around a non-enhancing clot
• MR venography is the investigation of choice, showing absent flow and the extent of propagation into the jugular vein
• Antibiotics mask the classical picture, so a patient merely failing to improve deserves venography rather than reassurance
• Anaemia is characteristic of the prolonged septic course and should be corrected alongside the antibiotic
• The sinus need not be opened routinely; drainage of the perisinus infection with antibiotics suffices
• Jugular ligation is now rarely performed, and is reserved for continuing septic emboli despite adequate treatment
• Anticoagulation remains controversial and is used selectively, balancing propagation against haemorrhage
• Septic emboli lodge in the lungs first, causing abscesses and empyema, so a chest film is part of the assessment
• Palpate the neck for a tender cord along the internal jugular vein.