Neuroradiology Case of the Week

Case 2

Matthew Cham, MD and and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 55-year-old patient with breast cancer presented with swallowing difficulties.

Radiologic Findings: Axial and sagittal MR sequences demonstrate a well-circumscibed lesion involving the right clivus and hypoglossal canal, which is isointense on T1-weighted sequences (Figs. 1 & 2). Post-gadolinium sequences demonstrate enhancement of this lesion, which measures about 2.6 cm x 1.5 cm (Figs. 3 & 4).

Figure 1	Figure 2
Figure 3	Figure 4

Diagnosis: Metastatic disease to hypoglossal canal and clivus

Discussion: For focal neurologic symptoms such as swallowing difficulties, MRI of the brain as well as skull base are indicated. In this case, there was a focal lesion invading the hypoglossal canal, explaining the patient’s focal neurologic symptoms.
   The hypoglossal canal is the pathway through which the motor neurons of the hypoglossal nerve, originating from the hypoglossal nucleus in the medulla oblongata, innervate both the extrinsic and intrinsic muscles of the tongue.
   The motor division is important in the coordinated contraction of different parts of the tongue required for activities such as food manipulation, swallowing, and speech. Damage to the hypoglossal nerve pathway or its associated nuclei may result in dysarthria or dysphagia, the latter of which was observed in our patient.
   Many unrelated tumors occur in the skull base, and include a variety of primary tumors and metastatic disease. Skull base tumors can also be categorized into those that occur throughout the skull base and those that are unique to a particular area.
   Malignant tumors that occur throughout the skull include metastatic lesions to the bone, whereas benign tumors include meningiomas, schwannomas, and osteomas.
   In this patient with an enhancing lesion in the clivus and hypoglossal canal, skull base tumors that are unique to these areas must also be considered in the differential. Middle cranial base tumors are often benign, and include craniopharyngiomas, temporal bone tumors, and enchondromas. Posterior cranial fossa tumors may be malignant, such as a chondrosarcoma, or benign such as chondromas, and chordomas.
   Treatments for skull base tumors can be divided into medical, radiation, and surgical. These treatments also apply to benign lesions that cause persistent or progressive symptoms due to uncontrolled growth.
   This patient has metastatic breast cancer, which is the most common cause of bone metastasis in women. This skull base lesion was subsequently treated with radiation therapy for symptomatic relief of the patient’s dysphagia.

References:

1. Flickinger FW, Sanal SM: Bone marrow MRI: techniques and accuracy for detecting breast cancer metastases. Magn Reson Imaging 1994; 12(6): 829-35.
2. Hortobagyi GN, Libshitz HI, Seabold JE: Osseous metastases of breast cancer. Clinical, biochemical, radiographic, and scintigraphic evaluation of response to therapy. Cancer 1984 Feb 1; 53(3): 577-82.
3. Jones AL, Williams MP, Powles TJ, et al: Magnetic resonance imaging in the detection of skeletal metastases in patients with breast cancer. Br J Cancer 1990 Aug; 62(2): 296-8.
4. Long DM: Surgical approaches to the skull base: an overview. Neurosurgery 1996; II: 1573-1584.