Angiolipoma

The first spinal angiolipoma was described by Berenbruch in 1890.1,13 Andaluz et al have recently reviewed the subject of angiolipomas within the CNS.1 They reported 94 documented cases: 86 within the spinal canal (predominantly extradural) and 8 found intracranially.1 Table 37-3 outlines the 8 reported intracranial angiolipomas.

The majority of cases of spinal angiolipomas are found in the posterior epidural compartment. This is in contrast to the infiltrating angiolipomas that occur more commonly in the anterior epidural space. More than 75% of the reported spinal canal cases occurred along the thoracic spine, the majority involving three or more spinal segments.1,13 The intracranial angiolipomas appear too infrequently to make any generalizations regarding their most common locations (see Table 37-3).

The presentation of angiolipomas both intracranially and within the spinal canal may be more acute than that of the spinal cord lipomas and intracranial lipomas. Most patients seek treatment less than 1 year after the onset of symptoms. Long and fluctuating courses, however, are not unheard of, making the diagnosis more difficult. The acute precipitation of symptoms, in the case of angiolipomas, is likely related to complications within their vascular component, such as hemorrhage, thrombosis, vascular engorgement, and vascular steal.1,13 Pregnancy has also been noted to precipitate symptoms from spinal and intracranial angiolipomas.1 Like other mass lesions of the CNS, the size and location of the angiolipoma will dictate neurologic signs and symptoms.

The epidemiology of angiolipomas is difficult to trace because there are no clear-cut diagnostic criteria to define them. Some authors have suggested that if "lipomas and heman-giomas truly represent the limits of the same pathologic spectrum, angiolipoma, angiolipoma with erosion, and infiltrating angiolipoma may represent intermediate steps."13 In addition, it would appear that some pathologists may use the term angi-olipoma for capillary hemangiomas with a lipomatous component, whereas others diagnose highly vascularized lipomas as angiolipomas. According to the available published data, angi-olipomas, as a group, account for 0.14% to 1.2% of all spinal tumors.1,13 Based on the list accumulated by Andaluz et al,1 it appears that angiolipomas are found more commonly in women

Table 37-3

Intracranial Angiolipomas Reported to Date

Study

Takeuchi, 1980

Wilkins, 1987 Lach, 1994 Shuangshoti, 1995 Prabu, 1995 Prabu, 1995 Murakami, 1997 Andaluz, 2000

Patient Age and Sex

72-yr-old female

60-yr-old 65-yr-old

25-yr-old

26-yr-old

28-yr-old 31-yr-old

29-yr-old female female male female male male female

Location

Suprasellar or parasellar

Parasellar

Suprasellar

Thalamic

Frontoparietal

Internal auditory canal Frontal

Presenting Symptoms

Acute subarachnoid hemorrhage and associated aneurysms Seizures

Hypopituitarism, cranial nerve deficit

Acute hemorrhage

Seizures

Deafness, ataxia, lower cranial nerve deficits

Recurrent acute hearing loss

Seizures

CPA, Cerebellopontine angle.

(Modified from Andaluz N, Balko G, Bui H, Zuccarello M: Angiolipomas of the central nervous system. J Neurooncol 49:219-230, 2000.)

than men (1.65:1), presenting most commonly in the fourth or fifth decades of life. The mean age of presentation was 43 years in both the infiltrating and noninfiltrating spinal angiolipoma groups. No statistical analysis was performed on the intracra-nial angiolipoma group given the small sample size.

As mentioned previously, lipomatous tumors have a characteristic appearance on CT and MRI and angiolipomas are no exception. However, variations in the appearance of these tumors may be related to their intense vascularity, with their individual appearance on MRI dependent on the relative contributions of adipose tissue and vasculature within the tumor. Interestingly, angiolipomas tend not to show flow voids on MRI. This may be related to the relatively high density of slow-flow capillary and venous channels within them. Infiltrating angiolipomas may produce trabeculated patterns within vertebral bodies, in some cases resembling hemangiomas; however, angiolipomas do not show late enhancement with contrast.1

Therapy has generally consisted of surgery, by way of a posterior approach, as in the case of intraspinal lipomas. There are no documented cases of radiation therapy or chemotherapy used for treatment of these benign lesions. Recurrence has not been documented to occur. Once the tumor is removed, the prognosis is generally good, with most patients achieving near-complete or complete recovery.1,13

the 35-year-old woman had motor weakness and numbness of the left upper extremity.4,17 The 33-year-old woman with the parasagittal hibernoma had partial motor seizures.21

Radiographic imaging of hibernomas is similar to other lipomatous tumors. The L3 to L5 lesion was discovered on myelogram in the pre-CT era, and the cervical lesion was noted to be highly vascular, appearing more like an angiolipoma. This latter lesion was noted to be hyperintense on both T1- and T2-weighted MRI scans and markedly contrast enhanced. The intracranial hibernoma was suspected on carotid angiography.

Grossly, hibernomas are well encapsulated and slightly dark-yellow to red-brown. Surgical specimens are required to make the correct final diagnosis.4,21 Histologically, hibernomas are composed of brown adipose tissue, considered to be an immature form of white adipose tissue. These tumors are generally positive for S-100 protein as are normal fat cells. Combined hibernoma and lipomas are probably more common than pure hibernomas.4

Therapy for hibernomas consists of surgical resection. In contrast to intracranial and intraspinal lipomas, these tumors are easily separable from the surrounding tissue. Recurrence is rare, given their benign nature. However, there is one questionable report of a malignant hibernoma.21 Standard postoperative follow-up is likely adequate.

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