MR imaging of the trigeminal ganglion, nerve, and the perineural vascular plexus: normal appearance and variants with correlation to cadaver specimens.

BACKGROUND AND PURPOSE: MR imaging is the method of choice for evaluating the trigeminal nerve. Detection of abnormalities such as perineural tumor spread requires detailed knowledge of the normal MR appearance of the trigeminal nerve and surrounding structures. The purpose of this study was to clarify the normal MR appearance and variations of the trigeminal ganglion, maxillary nerve (V2), and mandibular nerve (V3) with their corresponding perineural vascular plexus. METHOD: S: MR images obtained in 32 patients without symptoms referable to the trigeminal nerve were retrospectively reviewed. The trigeminal ganglion in Meckel's cave, V2 within the foramen rotundum, and V3 at the level of foramen ovale were assessed for visualization and enhancement. The configuration of the perineural vascular plexus was recorded. Correlation to cadaver specimens was made. RESULTS: The trigeminal ganglion and V3 were observed to enhance in 3-4% of patients unilaterally. V2 and V3 were well visualized 93% of the time. The perineural vascular plexus of V2 was observed 91% of the time, and that of V3 in 97% of instances. CONCLUSION: This study characterizes the normal MR appearance of the trigeminal ganglion and its proximal branches. The trigeminal ganglion, V2, and, V3 are almost always reliably seen on thin-section MR studies of the skull base. Enhancement of the perivascular plexus is routinely seen; however, enhancement of the trigeminal ganglion, V2, or V3 alone is seen only on occasion as supported by the avascular appearance of these anatomic structures in cadaver specimens.

Carcinoma of the skin of the head and neck with perineural invasion.

BACKGROUND: Perineural invasion is observed in a small subset of patients with carcinomas of the skin of the head and neck. METHODS: Review of the patient literature highlighting the University of Florida experience. RESULTS: Patients with early perineural invasion are asymptomatic, and the phenomenon is discovered only on pathologic examination of the excised lesion. These patients are defined as having "incidental" perineural invasion, and treatment with surgery followed by postoperative irradiation results in a cure rate of approximately 80%. Undiagnosed, the perineural carcinoma slowly progresses and eventually results in symptoms, usually facial weakness or numbness. The disease eventually extends to the skull base and becomes incompletely resectable. Symptomatic patients are defined as having "clinical" perineural invasion, and aggressive treatment results in a cure rate of approximately 45%. CONCLUSIONS: Perineural invasion is an uncommon spread pattern observed in patients with skin cancer and is associated with a relatively poor prognosis. The likelihood of cure is inversely related to the proximal extent of the cancer and is lower for symptomatic compared with asymptomatic patients.

Carcinoma of the skin with perineural invasion.

PURPOSE: To evaluate the outcome and patterns of relapse in patients treated for skin carcinoma of the head and neck with either microscopic or clinical perineural invasion. METHODS AND MATERIALS: Radiotherapy alone or combined with surgery was used to treat 135 patients with microscopic or clinical evidence of perineural invasion of skin carcinoma. All patients had at least 2 years of follow-up. RESULTS: The 5-year local control rates without salvage therapy were 87% with microscopic perineural invasion and 55% with clinical perineural invasion. Overall, 88% of the local failures occurred in patients with positive margins. Almost half of the recurrences in patients with microscopic perineural invasion were limited to the first-echelon regional nodes. However, only 1 of 11 patients with basal cell carcinoma with microscopic perineural invasion had a nodal failure. Ninety percent of recurrences in patients with clinical perineural invasion occurred at the primary site. Cranial nerve deficits rarely improved after successful treatment of the primary disease. Radiographic abnormalities remained stable 30% of the time when patients had clinical evidence of progressive disease. CONCLUSIONS: Radiotherapy in patients with skin cancer with clinical perineural invasion should include treatment of the first-echelon regional lymphatics. The risk of regional node involvement is also relatively high for patients with squamous cell carcinoma with microscopic perineural invasion. In patients with clinical perineural invasion, the poor local control rates with conventional radiotherapy suggest a need for dose escalation with or without concomitant chemotherapy.