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Show ]. Clin. Neuro-ophthalmoJ. 1: 57-62, 1981. Neuroradiological Clinical Pathological Correlations Unilateral Sixth Nerve Paresis ROBERT M. QUENCER, M.D. Author's Note The object of the qu~rterly Neuroradiologic CPC is to prnent cases of neuro-ophthalmological interest in which ~ differentiill diilgnosis can be formul~ted on the Nsis of the radiological information supplied. F~l1owingeilch case history, the pertinent rildiographs will be shown ilnd the use discussed. A short bibliog~ phy will be included. Each presenulion will be tilled by its predomin~nt cliniul feilture; however, in the index ilt the end of eilch volume, the epe's will also be listed by their pathological diagnosis. Robert M. Quencer, M.D. Case History . A 57-year-old previously healthy female expenenced the sudden onset of horizontal diplopia without associated headache or eye pain 5 months prior to her current hospitalization. The diplopia gradually improved over the next 20 days, and she remained symptom-free until just prior to admission when the diplopia recurred. The diplopia was constant and unrelated to the time of day. The patient was otherwise well with no history of thyroid dysfunction, diabetes mellitus, weight loss, headaches, loss of consciousness, or vision loss. On examination, she was found to have a left sixth nerve paresis with nonnal visual acuity and visual fields. Tensilon test was negative and the fasting blood sugar level and the sedimentation rate were nonnal. A skeletal survey and bone scan for evidence of other bone lesions were negative. The radiographic evaluation included plain skull films (Fig. 1), computed tomography (Fig. 2), cerebral angiography (Fig. 3), and metrizamide cisternography (Fig. 4). From the Department of Radiology, University of Miami School of Medicine, Miami, Florida. March 1981 Discussion Based on the plain skull findings (Fig. 1) of destruction of the dorsum sella and upper clivus and a soft-tissue mass in the posterior portion of the sphenoid sinus, a number of possibilities may be considered in the differential diagnosis, namely: ~eningioma; pituitary neoplasm; a neoplasm aris109 from the sphenoid sinus or nasopharynx; metastasis; a neoplasm arising from the bone at skull base such as a plasmacytoma, chondrosarcoma, or a chordoma. Each of these entities is considered below. A meningioma would be unlikely because three c~~mon features of meningioma are missing. SpeCifICally: there is no bony hyperostosis (Fig. I), the CT scan (Fig. 2) shows no evidence of tumoral enhancement, and the angiogram (Fig. 3) does not s~o~ a homogenous tumor stain. A large primary pituitary neoplasm would have caused diffuse enlargement or destruction of the sella turcica not the very focal destructive changes seen in this case. A neoplasm such as a lymphoma, sarcoma, or carcinoma arising from the sphenoid sinus or nasopharynx would be expected either to cause a softtissue mass in the entire sphenoid sinus or to cause a mass in nasopharynx before bone destruction would occur. A metastatic deposit is possible, on the basis of the radiographs, but clinically the lack of progressive or new symptoms over a 5-month period makes a metastasis a poor consideration. This leaves a tumor arising from the bones of the skull base as the probable cause of the patient's symptoms. The skull base develops from cartilage and a chondrosarcoma must be conSidered; however, the typical cartilagenous calcification seen in that type of neoplasm is not present. Since this location would be a very unusual location for a plasmocytoma, a clivus chordoma should be the primary diagnostic consideration. Chordomas arise from intra-osseous notochordal remnants, and the vast majority are found intracranially or in the sacrococcygeal region. Over 57 Figure 1. Lateral skull. There is destruction of the up""r portion of the clivus. dorsum sella. and posterior floor of the sella turcica. The normal lower portion of the clivus is outlined by arrowheads. while the sella floor IS nonndl anterior to white- arrow, A soft4 lissue mass IS present In the posterior sphenoid sinus. March 1981 161 Figures 3~-3c. Cerebral angiography. Left internal carotid dnl\iol\ram (,,) shows bowing of the precavernous portIon of the carotid artery ( urved arrow). closinl\ of the carotid siphon (between stra ij(ht arrows). and faint neovascul",ity (between arrowheads) arising from the distal precavernous carotid. These findinl\s sUl\8est Ihe presence of an extradural mass. No tumor slain was present. The arterial phase of the left vertebral angiogram (b) IS deliberately not subtra("ted 0 thdl the posterior displa("ement of the basilar artery (drrowl aWdY from the clivus can be dppredated. On the venous phase of the left vertebral angiogrdm (c) the prepontine mdSS (MI is capped by ("ontrast in the basildr venous plexus. uencer 59 Unilaler.,1 Sixth Nerv(' PM('sis I.) Figure 3. (Continued.) 50% of cranial chordomas occur in the clivus and although they may present at any age, the onset of symptoms before puberty is unusual. The presenting symptoms are related to compression by the tumor of the brain stem or the adjacent cranial nerves. Facial or neck pain, limb paresis, ataxia, and headaches may be present, but are almost always seen in conjunctic;; with peripheral cranial nerve dysfunction. The size of the tumor and the direction of its growth will determine whether there are unilateral or bilateral symptoms. Because chordomas may infrequently arise in other portions of the skull base besides the clivus, chordomas must be considered in the differential diagnosis of extradural bony lesions in the cerebellopontine angle, the parasellar region, and at the foramen magnum. The hallmark of a chordoma is bone destruction (over 95% of cases), so without that finding the diagnosis of a chordoma should be considered unlikely. Radiographic demonstration of a softtissue mass either in the nasopharynx or in the sphenoid sinus, tumoral calcification, and bony sclerosis are auxiliary findings in chordoma, but it should be stressed that since these features are present in a minority of cases, bone destruction 60 alone along the base of the skull is sufficient to consider chordoma a diagnostic possibility. When a clivus chordoma becomes large, there may be extensive destruction of the sphenoid bone and sella turcica, unlike the focal bone destruction seen in the case presented here. In chordomas, computed tomography is capable of demonstrating bone destruction, calcification, sclerosis, and a soft-tissue mass which mayor may not enhance. It is obvious in comparing Figures 1 and 2 that the plain skull films may be clearly abnormal while the CT abnormalities are quite subtle. This is particularly true when a small, noncalcified chordoma is located in the dorsum sella, or clivus. In these cases, metrizamide cistemography with routine tomography (Fig. 4.1) or combined with computed tomography (Fig. 4b) is the most sensitive study in outlining the precise size and extent of the intracranial portion of the mass. This information is important in presurgical planning, whether a craniotomy or a trans-sphenoidal biopsy is to be performed. Cerebral angiography (Fig. 3) will show vascular displacement, tumor vascularity. and encasement by the chordoma of the major arteries at the skull base. Journal of Clinical Neuro-ophthalmology March 1981 1.1 1.1 Figur~s 4~ ~nd 4b. MetriZdmide cisternography: Five cubic c~ntim.ters of metriZdmide (300 mg/cc) was introduced Into the lumbar subarachnoid space and was presented to the ventral cisternal subarachnoid spaces. Linear tomography (a) and computed tomography (b) shows a moss (arrows in a and b) displacing the subarachnoid space away from the clivus. 61 62 Unilateral Sixth Nerve Paresis In the patient presented here, a biopsy via a trans-sphenoidal approach was performed. Histopathological examination was typical of a chordoma. A course of radiation therapy (6000 rads in 6 weeks) to the skull base was given. References 1. Kendall. B.E., and Lee, B.C.P.: Cranial chordomas. 8r. f. Rddio/. so: 687-698, 1977. 2. Smink, K.W.F., Hekster, R.E.M., and Bots, G.T.A.M.: Clivus chordoma with distinct vascularity demonstrated by angiography. NeuroradioJogy 13: 273-277, 1977. Write For reprints to: Robert M. Quencer, M.D., Department of Radiology (R-130), University of Miami, School of Medicine, P. O. Box 016960, Miami, Florida 33101. Journal of Clinical Neuro-ophthalmology |
