I. BRAHIM, A. DARDIK, S. BOURKHIS, F. BEN AMARA, H. RAJHI, N. MNIF Department of Radiology Charles Nicolle Hospital, Tunis, Tunisia NR22

 Describe the clinical and imaging features of facial plexiform nevroma  Distinguish them from vascular malformation and lymphangioma  Precise their management.

 A 37-year-old man  Neurofibromatosis type 1 (von Recklinghausen’s disease)  A swelling on the left side of the face -since 10 years -had an insidious onset -it had grown slowly to attain the present size.  Mild, intermittent dull aching pain in the swelling since 1 year.  No history of any regression or any discharge from the swelling.

 Extra oral examination : a swelling -Diffuse on the left side of the face over the jugal region. -Measured approximatively 5x5 cm in size - Indistinct borders. -Mild tenderness -Peculiar consistency, soft in most of the areas with few firm nodular areas, as a 'bag of worms'. -No pitting -On auscultation : no bruit

AX T1 AX T2 CORO T2 AX T2 FATSAT MRI IMAGES show : -hemifacial infiltrating, ill-defined mass ( pink arrow). - With homogeneous signal intensity lesion - The lesion appeared isointense in T1W images and hyperintense in T2W images with few flow voids (red arrow) within the lesion

AX T1 FATSAT AX T1 FAT SAT GADO CORO T1 FAT SAT GADO MRI IMAGES show : The lesion (pink arrow) extends to the parotid lodge, the infratemporal fossa, parapharyngeal, masticator, carotid, posterior cervical spaces and enhanced homogeneously and intensively after Gadolinium injection

 Typically occurs in the setting of neurofibromatosis type 1 (NF1) and is included in the criteria for its diagnosis.  Considered pathognomanic of NF1.  May be associated with other stigmata of NF1, or it may appear as an isolated lesion.  Is a non metastasizing and locally invasive tumor  Causes diffuse enlargement of skin, subcutaneous tissue and nerve segments of the affected areas.

 Is a benign nerve tumor resulting from aberrant growth of the cells of the nerve sheath.  Originates from the central aspect of the nerve and involves multiple fascicles.  Composed of schwann cells, perineurial-like cells, and fibroblasts.  Although the fascicles are usually preserved, a diffusely enlarged, thickened, irregular, and tortuous nerve is produced.

 Is classically compared to a "bag of worms" or "rosary beads".  Is a type of multinodular growth of tumor that forms along nerves plexus or a single large peripheral nerve.  Presents a tangle of irregularly sized and smooth nodules.  Sausage like enlargement or rope-like alteration of the affected nerve is seen in single nerve involvement.

 Any cranial or peripheral nerve is susceptible to PNF formation.  There is a predilection for larger peripheral nerves of the face, neck and extremities.  Motor and sensory nerves from the oculomotor to the hypoglossal, as well as sympathetic and brachial plexus involvement in the neck leading to Horner’s syndrome and motor palsy.

 Can be deep, superficial or a combination of both.  Superficial PNF are : - more common than the deep lesions, - more likely to be asymmetric in distribution, with a diffuse or infiltrating morphology, extend to the skin surface in a reticular and branching pattern, with smaller fascicles or nodules. - can be mistaken for venous malformations.

 Can assume rather large proportions and involve multiple nerves.  As a result of tumor growth, adjacent bone resorption and soft tissues hyperplasia can occur.  The involved nerves may be very distorted, and often totally replaced and unrecognizable.  The destruction of bony landmarks can make the identification of the facial trunk a delicate and dangerous task.

 Usually present since birth and may develop throughout life.  Is typically painless and may go unnoticed until it become palpable or cause dysfunction of surrounding structures.  Usually becomes symptomatic at an early age and exhibits progressive growth.  Increased growth rates occur during childhood or hormonal changes, such as puberty or pregnancy.  Trauma is thought to be an inciting factor, but no clear association has been made.

 Is easy to identify on clinical examination because it feels like a “bag of worms” or “peas in a pod” along involved nerves  Overlying skin and soft tissue may undergo hypertrophy as well as pigmentary changes (orange discoloration)  May have dramatic effects on surrounding skin, soft tissues, and osseous architecture.  The presence of PNF of the head and neck may interfere with the nasal airway, the eyelids, vision, mastication, and lip competence, in addition to producing a cosmetic deformity.

 The most distinctive lesion in neurofibromatosis is plexiform neurofibroma.  These lesions may obtain a massive size.  Appear either well defined (surrounded by a thick perineurium) or loosely arranged with limits impossible to define.

 Nonenhanced CT scans typically reveal low attenuation masses (3O HU) with ill-defined margins.  Low attenuation of the lesions may due to: -the high water content of the mucinous matrix -the lipid nature of Schwann cells -the cystic degeneration and incorporation of surrounding adipose tissue into the masses.  Peripheral enhancement after intravenous administration of contrast material and calcifications are nonspecific findings.

 On T1-weighted images : - signal intensity slightly greater than that of muscle. - hyperintense septations due to myelinated axons  On T2-weighted images : - markedly increased signal intensity is seen (high water content ) - hypointense septations corresponding to collagen fibers - a central zone of lower signal intensity, coined the "target sign" -This central inhomogeneity is due to hemorrhage, fibrosis, necrosis, and/or variations in cellularity This may prove to be a useful feature in distinguishing neurofibromas from other soft-tissue tumors.

 Is the modality of choice for the evaluation of soft-tissue tumors.  Has demonstrated superiority over CT in the evaluation of soft tissue tumors.’  PNF typically reveals a noncharacteristic appearance and is often misdiagnosed when a history of NF1 is unclear.  When the MRI appearance is typical, it suggests the diagnosis.

 Is able to distinguish thickened perineurium (fibrous tissue) surrounding the plexiform neurofibroma.  Its multiplanar capabilities precise volumetric evaluation of the PNF which is helpful in delineating the extent of the tumor.  Its ability to distinguish benign from malignant neuronal tumors remains poor.  May not detect osseous invasion.

 PNF differ from schwannoma and neurofibroma, in that the former are unencapsulated and involve several fascicles rendering their internal margins almost indistinguishable  Unfortunately, there is no radiographic study able to definitively distinguish between them. Lymphoma Schwannomas Neurofibromas Malignant peripheral nerve sheath tumors

 Macroscopic appearance : -Ropelike : non branching nerves -Bag of worms : highly branching nerves  Classified into 2 types: Nodular (common) / Diffuse (rare)  A benign nerve sheath tumor, non encapsulated, poorly circumscribed that often extends tortuously along nerves.

 Proliferation of spindle cells from either the neuroectodermal Schwann cell sheath or mesodermal fibrous connective tissue.  A myxoid matrix is typical of PNF however, as these tumors enlarge, they become more cellular and collagenous  PNF cells are usually S-100 positive (immunohistochemical marker )

 Sarcomatous transformation is suggested when a soft tissue mass becomes symptomatic : rapid growth and pain.  Between 5 and 6% of PNF undergo malignant transformation, known as malignant peripheral nerve sheath tumour (MPNST).

 The immediate clinical problem depends on location.  When the lesion involves the upper airway, there is strider and obstruction early in infancy. Tracheotomy and removal of all tumor possible offer the only hope for survival in this group of patients.

 MRI is ideal for routine follow-up in : no ionizing radiation and noninvasive,  Indications for long-term follow-up : - malignant transformation, - rapid recurrence after excision - rapid growth.

 Indications for surgical intervention (definitive treatment ): pain, dysfunction, diagnostic biopsy, and/or suspected malignancy.  Radical surgery is unnecessary and usually impossible to perform because of the extent of the tumor.  We recommend selective conservative surgical resection of functionally impairing or cosmetically deforming masses without the removal of nerves that control important functions.  Surgical resection of PNF is complicated by a high rate of recurrence.

 Considered pathognomanic of NF1.  A benign nerve and locally invasive tumor.  Classically compared to a "bag of worms".  Has predilection for nerves of the neck, face and extremities.  MRI is the modality of choice for suggesting the diagnosis when the apperance is typical and for the follow-up.  Selective conservative surgical resection is recommended.

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