INCIDENTAL NEUROPATHOLOGICAL FINDINGS IN A CHILD WITH CERVICAL MENINGORADICULOCELE

Clinical History

After an uncomplicated pregnancy and birth an otherwise healthy girl showed a skin appendix in the dorsal mid‐cervical region. The lesion was notable in prenatal routine ultrasound examination at the 19^th gestational week (Fig. 1A, arrow). Family history was negative for neurodevelopmental pathologies. A primary ultrasound examination revealed a connection with the cervical spinal cord. The consecutive MRI of the neuroaxis confirmed a dorsal connection of the skin malformation with a dysplastic cord in the related segments (Fig 1B, arrow). The brain scans demonstrated multiple subependymal heterotopias. EEG did not detect any epileptogenic foci. Clinically, no epileptic seizures have occurred. After a follow up of 18 months a significant motor developmental delay was noticed. Speech development was above average. At the age of 2 months the little girl underwent plastic surgery for a dysraphic malformation of the cervical cord with resection of a skin appendix (Fig. 1 C) and removal of tethering structures at the dysplastic cervical cord at level C6. Dura mater and skin were closed without complication. The postoperative course was uneventful. No signs of re‐tethering were found in long‐term follow up. The resected tethering structures were sampled and sent for further histopathological analysis.

Figure 1.

 

Histopathological Features

Grossly, the material consisted of small fragments of adipose and fibrous tissue, partially covered by skin. The microscopic examination revealed fibro‐adipose tissue containing numerous nerve fascicles with degenerative features (Fig. 2, arrows). Along the nerve fascicles, a 0,7 cm large nodule‐like lesion composed by “onions bulbs”‐like structures with up to 10 concentric lamellae and one or more centrally placed axons (Fig. 3, 4, 5; Fig. 3 Masson‐Trichrome stain) were present. The cells surrounding the axons appeared focally densely packed (Fig. 6). The axons were labelled with neurofilament antibody (NFP) (Fig. 7a) and surrounded, also in more cellular areas, by S‐100 (Fig. 6b) as well as GLUT‐1 positive Schwann cells. EMA staining was present only in the outer layer of “onion bulbs” (Fig. 7c). The proliferation index evaluated with MIB‐1 antibody reached a value up to 1%, restricted to few lymphocytes. The nerve fascicles were embedded within fibrotic meningeal tissue.

Figure 2.

 

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Figure 6.

 

Figure 7.

 

Diagnosis

Pacinian hyperplasia (“Pacinioma”, pacinian neuroma) associated with meningoradiculocele.

Discussion

Dysraphic conditions of the spine resulting from non‐closure of the neural tube comprise a wide spectrum of different types of malformations. In meningoradiculocele the nerve roots are components of the herniated cystic structure. The material that usually is submitted to histological examination may contain various amounts of soft tissue (including adipose tissue) and meninges 1, 2, 5, 6. Nerve structures are frequently encountered and may vary from easily identifiable large myelinated nerve trunks to small nerve fascicles with moderately increased numbers of fibres compared to those normally present. Very rarely, these structures may present “neuroma‐like” features with proliferation of Schwann cells, or pacinian corpuscles hyperplasia with “onion bulbs” features 1, 2, 5, 6.

Hypertrophy and hyperplasia of pacinian corpuscles is a rare condition and occur mainly in adults 4, 7, 8. The preferential site of occurrence is the hand but some deep seeded localisations have been described 3, 8. Although history of local trauma was often reported, the pathogenesis of such a lesion is still unclear 8. Histologically, pacinian hyperplasia does not form large tumor‐like masses. The corpuscles have a normal structure but are increased in size and number. Sometimes they are dystrophic, with several lamellar bodies within a single capsule.

In the differential diagnosis, other lesion consisting of intraneural proliferation of perineural‐like cells may be considered. Intraneural perineurioma is characterized by a tumoral, fusiform segmental growth of nerve trunks and histologically composed by densely packed EMA positive perineurial cells which proliferate in pseudo‐onion bulb whorls around thin axons 9. In our case, the areas showing densely packed cells could resemble a “perineurioma‐like” architecture: however, the combined EMA negativity and S‐100 positivity indicate that these elements are reactive Schwann cell rather than real perineural cells.

Other nerve sheaths lesions or tumors, including neurofibroma, schwannoma and traumatic neuroma, may present a perineural onion bulb‐like structures but pure pacinian differentiation associated to nerve sheath tumors have not been demonstrated 3, 8.

In conclusion, pacinian hyperplasia may be rarely encountered in sample obtained from surgery for spina bifida malformations, and has not to be confused with other more common neoplastic lesions affecting the spinal cord region.

Abstract

After an uncomplicated pregnancy and birth an otherwise healthy girl showed a skin appendix in the dorsal mid‐cervical region with a connection to the cervical spinal cord. The lesion was notable in ultrasound examination at the 19^th gestational week. At the age of 2 months the patient underwent plastic surgery of a dysraphic malformation with resection of the skin appendix and removal of tethering structures at the dysplastic cervical cord at level C6. The histological examination revealed fibro‐adipose tissue containing numerous nerve fascicles with degenerative features. Along the nerve fascicles, a nodule‐like lesion composed of “onions bulbs”‐like structures with up to 10 concentric lamellae and one or more centrally placed axons was present. The cells surrounding the axons appeared focally densely packed. The lesion was compatible with the diagnosis of Pacinian hyperplasia (“Pacinioma”, pacinian neuroma) associated with meningoradiculocele.

Although Pacinian hyperplasia occurs preferentially in the hand, some deep seeded localisations have been described and encountered in samples obtained from surgery for spina bifida malformations. Pacinian hyperplasia has not to be confused with other more common neoplastic lesions affecting the spinal cord region.