Abstract
INTRODUCTION: Tarlov first described the sacral perineural cyst in 1938 as an incidental finding at autopsy. There is very little data in the literature regarding the natural history of Tarlov cysts and consequently the recommendations for treatment are vague. Various operative treatments have been suggested including cyst aspiration, cyst decompression, microsurgical cyst imbrication and cyst plication with cement filling of bony defects. We were first presented with the difficulty of managing a patient with a large symptomatic sacral cyst in 1997 and found little in the literature to help advise the patient. This paper presents the results of a prospective observational study and describes the clinical relevance of the different types of cyst, showing how a simple clinico-radiological classification can be used to help manage patients with cysts.
METHODS: Between February 1997 and December 2002, 3935 patients underwent standard three sequence MRI scanning (T1 and T2 sagittals and T2 axials) for lumbosacral symptoms in our hospitals. 62 patients had cysts in their sacral canals, an incidence of 1.6%. Additional contiguous axial and coronal scan sequences were carried out to fully characterise them. Once identified, the clinical picture was correlated with the findings on MRI.
RESULTS: Tarlov cysts can be classified according to whether or not their presence is related to clinical symptoms. Type 1 cysts (n=38; 61%) are small, often multiple and are found at the most distal sacral segments. They are entirely unrelated to the patient’s symptoms and require no specific treatment. This has been confirmed when the primary pathology has been treated and the patient’s symptoms have been alleviated. Type 2 cysts (n=13; 21%) are usually single, unilateral and occur at the same level as the main cause of the patient’s symptoms, often a prolapsed intervertebral disc at L5/S1 with a Tarlov cyst in the S1 root canal. As such, the cyst itself will not require any treatment, which should be directed at the main pathology. Type 3 cysts (n=11; 18%) are the main cause of the patient’s symptoms and may require specific treatment. We have found that more than half of the Type 3 cysts can be managed expectantly with serial clinical and MRI review. However, the majority of these cysts (9 of 11) are massive and can cause both erosion of bone and compression of the lower sacral nerve roots. Three have to date required decompression to treat cauda equina symptoms.
CONCLUSIONS: The majority of Tarlov cysts are incidental findings on MRI. They may, however, either contribute to, or be responsible for, a patient’s symptoms. Our classification system addresses this and offers guidance on patient management.
These abstracts were prepared by Dr Robert J. Moore. Correspondence should be addressed to him at Spine Society of Australia, Institute of Medical and Veterinary Science, The Adelaide Centre for Spinal Research, Frome Road, Adelaide, South Australia 5000.
