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Septum posticum cysts: An uncommon cause of chronic back pain
2 7I
'HRONIC
~f Medicine,
posterior thoracic pain associated ,ain was relieved bv surgical removal of J to myelographically proven arachnoid cysts ly exacerbated and associated with radicular may provide pain relief for some patients.
Po
INTRODUCTION
of neur010gic findings, and because arachnoid cysts arc seldom considered in the a~at~i~i c~ we are ¢~SEi
46,year.old white woman :~as initially inured in 1964 whe~ she fell from a
272
Fig° 1. Supine spot film, anteroposterior and lateral position. Three distinct cysts are evident in the dorsal subarachnoid space between T6 and Ts.
horse. She complained of continuous posterior mid-thoracic pain which radiated to the left chest in the T6-T9 dermatomes. She was initially treated with analgesics without relief. Two years after her injur) ' an evaluation including prone myelography did not ascertain the etiology of her pain. For 4 more years she complained of continued pain and was treated only with analgesic medications. Her workup again included myelography in the prone position; no diagnosis was established. Ten years after her initial injury she was referred to the University of Washington Hospital in Seattle, with the tentative diagnosis of 'ruptured thoracic disc'. Upon admission she stated that the pain had increased in intensity during the past several years and was characterized as deep, barning, dysesthetic and unremitKing. More recently it had been accompanied by some numbness in the left posterior mid-thoracic region. The pain could be partially alleviated by lying supine. Her physical examination was normal except for hypaigesia restricted to the !eft T6-T9 regions in the territory of the posterior primary rami. The pain was uninfl~.tenced by Valsalva maneuver but was augmented by percussion over the paraspinous muscles
273
Fig. 2. Supine spot film, anteroposterior position upright. One small cyst retains Pantopaque and extends between T3 and T4 in the dorsal subarachnoid space.
at the T7 level. Routine radiologic examination of the thoracic spine was normal. Electromyography (EMG) of myotomes Cs-T10 did not demonstrate abnormalities. Complete blood count, sedimentation rate, serum electrolytes and chemistries, Venereal Disease Research Laboratory, urinalysis and rheumatoid factor were normal. A myelogram in the prone position was normal, however, supine views demonstrated at least 3 cysts from T6 to Ts (Fig. 1). The cysts filled with Pantopaque but could not be emptied in spite of a variety of manipulations. She subsequently underwent a T6-Ts thoracic laminectomy. At surgery the cysts were easily identified; some still contained Pantopaque. Several were noted to have thin arachnoid bands attaching to posterior thoracic roots. These bands were lysed and the cysts removed with the aid of the operating microscope. Histologic examination revealed the cyst walls to consist of loose fibrous tissue partially lined by a layer of flat to cuboidal epithelium without evidence of inflammation, hemorrhage, or malignancy. Postoperatively she was free of her back pain and did not require analgesics. Her neurological examination was normal at the time of discharge from the hospital.
274 CASE
2
A 52-year-old white woman was in good health until she was involved in a car accident in 1973 which resulted in the symptoms of posterior cervical and interscapular pain with rail, with analgesics and daf and cervical pain. She diation :~othe left supra: Hospital for evaluation significantly relieved by lying supine or in the left lateral decubitus ~osition, Physical examination demonstrated a region of hyperalgesia from T.~ to T6 on the left side within the distribution of the posterior prireary rami. Cervical and thoracic spine radiographs and standard iaboratory studies were normal. Electremyographic studies of the cervical and upper thoracic paras tqnous musc|e~ and the arms were normal. Myelography in the prone position was normal, but when the patient was placed in the supine position a septum posticum cyst filled at T3-% (Fig. 2). Manipulation of the patient's position failed to empty the cyst. There was a larger negative filling defect adjacent to the cyst, implying that the cyst formation was more extensive than the portion which had filled with Pantopaque. For the first 24 h after myelography the patient was in bed, but when she began to ambulate her pain suddenly disappeared. The next morning, thoracic spine radiographs revealed that the Pantopaque previously located in the cyst had returned to the lumbar region. The patient was discharged free of pain; however:, her symptoms recurred within one month. The patient has declined surgical therapy at the present time. DISCUSSION
The incidence of intradural dorsal arachnoid cysts is unkno~'n. This is; due in part to the use of the term 'arachnoid cyst' t o intradural cysts which involve t h e arachnoidi For example, some series have corn, bined perineural cysts, lateral arachnoid diverticula, and traumatic mening~e!es which result from brachial plexus root avulsions, Although the above all represent arachnoid structures which are cystic:;, their incidence and significance are distinct from cysts which lie within or associated with the septum posticumi The natural history of septum posticum cysts is also unclear' Unless they are large e~ough to cause symptoms of myelopathy they are frequently unnoticed on standard myeIography; this is especially true in the United States where t h e myelographic contrast material is routinely removed at the termination of the procedure and therefore su:gine views are not routinely obtained. In those patients ~andergoing supine myelogra?hy it is not uncommon to find cysts of the septum postiicum which are totally asymptomatic. The septu~l posticum is a normal anatomical structurei Cysts ~ithin it have been ascribed to such etiologic factors as trauma, inflammation, syphilis and congenital anomaly. In the first patient we specifically studied the CSF and tissue
275 ,; none was present. While interval between onset of invoke a cause and effect relationship between each of these patients' trauma and subsequent symptomatic cysts. there are si. cative if :the symptoms a r e less threatening. Teng and Rudner s stated that in selected patients they could obtain symptomatic relief by having the patients periodically place themseNes in the Trendelenberg position, but this does net seem to provide long term benefit. Cysts of the septum posticum may be asymptomatic; and since back and neck pain are frequent complaints, selection of patients for surgical excision should be cautious. We wish to emphasize the following diagnostic points: (1) the pain from such lesion,~ often has an anatomical distribution usually restricted to the mid- or upper thoracic regions, (2) the pain may be influenced by the patient's position with res~ct to gravity and uninfluenced by specific spine movements, (3) mild sensory abnormalities restricted to the region of pain may be present, (4) there is often percussion tenderness over the region of the cyst, and (5) the only definitive diagnostic study i s supine myelography. If the patient's anatomical region of symptomatology corresponds with a myelographically demonstrated arachnoid cyst then the relationship between the two is considerably strengthened. Segmental epidurat blocks in this region :may be a help in deciding if surgical decompression is indicated. ACKNOWLEDGEMENTS
Supported in part by U.S. Public Health Service Grant NS05211. We thank Ellsworth C. Alvord, Jr., M.D., and the Laboratory of Neuroiol of Medicine for assistance in inte~reting
REFERENCES
~r, Philadelphia, Pa., t969, pp. 105-IlO. s of the, spinal membranes and roots, Brit.
J.
sur !e Liquide Cdphalo.rachidien ou Cdrdbro-
4 Nair, V: K , and Gardner, W, J,, Isolated interruptlon ot spinothalamic tract by arachnoid cyst, Neurosurg~, 32 (1970)68~688. 5 Perret; G'; Green, Keller, J., Diagnosis arid trea~ ~ent of intradura| arachnoid cysts of ti~e ila, ft. Neurosurg., 35(1971)65-70. Britl & RadioL, 39(1966) 249,254. NeuroL (Chic:}; 2 (1960)226,234.
'HRONIC
~f Medicine,
posterior thoracic pain associated ,ain was relieved bv surgical removal of J to myelographically proven arachnoid cysts ly exacerbated and associated with radicular may provide pain relief for some patients.
Po
INTRODUCTION
of neur010gic findings, and because arachnoid cysts arc seldom considered in the a~at~i~i c~ we are ¢~SEi
46,year.old white woman :~as initially inured in 1964 whe~ she fell from a
272
Fig° 1. Supine spot film, anteroposterior and lateral position. Three distinct cysts are evident in the dorsal subarachnoid space between T6 and Ts.
horse. She complained of continuous posterior mid-thoracic pain which radiated to the left chest in the T6-T9 dermatomes. She was initially treated with analgesics without relief. Two years after her injur) ' an evaluation including prone myelography did not ascertain the etiology of her pain. For 4 more years she complained of continued pain and was treated only with analgesic medications. Her workup again included myelography in the prone position; no diagnosis was established. Ten years after her initial injury she was referred to the University of Washington Hospital in Seattle, with the tentative diagnosis of 'ruptured thoracic disc'. Upon admission she stated that the pain had increased in intensity during the past several years and was characterized as deep, barning, dysesthetic and unremitKing. More recently it had been accompanied by some numbness in the left posterior mid-thoracic region. The pain could be partially alleviated by lying supine. Her physical examination was normal except for hypaigesia restricted to the !eft T6-T9 regions in the territory of the posterior primary rami. The pain was uninfl~.tenced by Valsalva maneuver but was augmented by percussion over the paraspinous muscles
273
Fig. 2. Supine spot film, anteroposterior position upright. One small cyst retains Pantopaque and extends between T3 and T4 in the dorsal subarachnoid space.
at the T7 level. Routine radiologic examination of the thoracic spine was normal. Electromyography (EMG) of myotomes Cs-T10 did not demonstrate abnormalities. Complete blood count, sedimentation rate, serum electrolytes and chemistries, Venereal Disease Research Laboratory, urinalysis and rheumatoid factor were normal. A myelogram in the prone position was normal, however, supine views demonstrated at least 3 cysts from T6 to Ts (Fig. 1). The cysts filled with Pantopaque but could not be emptied in spite of a variety of manipulations. She subsequently underwent a T6-Ts thoracic laminectomy. At surgery the cysts were easily identified; some still contained Pantopaque. Several were noted to have thin arachnoid bands attaching to posterior thoracic roots. These bands were lysed and the cysts removed with the aid of the operating microscope. Histologic examination revealed the cyst walls to consist of loose fibrous tissue partially lined by a layer of flat to cuboidal epithelium without evidence of inflammation, hemorrhage, or malignancy. Postoperatively she was free of her back pain and did not require analgesics. Her neurological examination was normal at the time of discharge from the hospital.
274 CASE
2
A 52-year-old white woman was in good health until she was involved in a car accident in 1973 which resulted in the symptoms of posterior cervical and interscapular pain with rail, with analgesics and daf and cervical pain. She diation :~othe left supra: Hospital for evaluation significantly relieved by lying supine or in the left lateral decubitus ~osition, Physical examination demonstrated a region of hyperalgesia from T.~ to T6 on the left side within the distribution of the posterior prireary rami. Cervical and thoracic spine radiographs and standard iaboratory studies were normal. Electremyographic studies of the cervical and upper thoracic paras tqnous musc|e~ and the arms were normal. Myelography in the prone position was normal, but when the patient was placed in the supine position a septum posticum cyst filled at T3-% (Fig. 2). Manipulation of the patient's position failed to empty the cyst. There was a larger negative filling defect adjacent to the cyst, implying that the cyst formation was more extensive than the portion which had filled with Pantopaque. For the first 24 h after myelography the patient was in bed, but when she began to ambulate her pain suddenly disappeared. The next morning, thoracic spine radiographs revealed that the Pantopaque previously located in the cyst had returned to the lumbar region. The patient was discharged free of pain; however:, her symptoms recurred within one month. The patient has declined surgical therapy at the present time. DISCUSSION
The incidence of intradural dorsal arachnoid cysts is unkno~'n. This is; due in part to the use of the term 'arachnoid cyst' t o intradural cysts which involve t h e arachnoidi For example, some series have corn, bined perineural cysts, lateral arachnoid diverticula, and traumatic mening~e!es which result from brachial plexus root avulsions, Although the above all represent arachnoid structures which are cystic:;, their incidence and significance are distinct from cysts which lie within or associated with the septum posticumi The natural history of septum posticum cysts is also unclear' Unless they are large e~ough to cause symptoms of myelopathy they are frequently unnoticed on standard myeIography; this is especially true in the United States where t h e myelographic contrast material is routinely removed at the termination of the procedure and therefore su:gine views are not routinely obtained. In those patients ~andergoing supine myelogra?hy it is not uncommon to find cysts of the septum postiicum which are totally asymptomatic. The septu~l posticum is a normal anatomical structurei Cysts ~ithin it have been ascribed to such etiologic factors as trauma, inflammation, syphilis and congenital anomaly. In the first patient we specifically studied the CSF and tissue
275 ,; none was present. While interval between onset of invoke a cause and effect relationship between each of these patients' trauma and subsequent symptomatic cysts. there are si. cative if :the symptoms a r e less threatening. Teng and Rudner s stated that in selected patients they could obtain symptomatic relief by having the patients periodically place themseNes in the Trendelenberg position, but this does net seem to provide long term benefit. Cysts of the septum posticum may be asymptomatic; and since back and neck pain are frequent complaints, selection of patients for surgical excision should be cautious. We wish to emphasize the following diagnostic points: (1) the pain from such lesion,~ often has an anatomical distribution usually restricted to the mid- or upper thoracic regions, (2) the pain may be influenced by the patient's position with res~ct to gravity and uninfluenced by specific spine movements, (3) mild sensory abnormalities restricted to the region of pain may be present, (4) there is often percussion tenderness over the region of the cyst, and (5) the only definitive diagnostic study i s supine myelography. If the patient's anatomical region of symptomatology corresponds with a myelographically demonstrated arachnoid cyst then the relationship between the two is considerably strengthened. Segmental epidurat blocks in this region :may be a help in deciding if surgical decompression is indicated. ACKNOWLEDGEMENTS
Supported in part by U.S. Public Health Service Grant NS05211. We thank Ellsworth C. Alvord, Jr., M.D., and the Laboratory of Neuroiol of Medicine for assistance in inte~reting
REFERENCES
~r, Philadelphia, Pa., t969, pp. 105-IlO. s of the, spinal membranes and roots, Brit.
J.
sur !e Liquide Cdphalo.rachidien ou Cdrdbro-
4 Nair, V: K , and Gardner, W, J,, Isolated interruptlon ot spinothalamic tract by arachnoid cyst, Neurosurg~, 32 (1970)68~688. 5 Perret; G'; Green, Keller, J., Diagnosis arid trea~ ~ent of intradura| arachnoid cysts of ti~e ila, ft. Neurosurg., 35(1971)65-70. Britl & RadioL, 39(1966) 249,254. NeuroL (Chic:}; 2 (1960)226,234.