Neuro

Question 1

Chiari 1

Answer 1

• cervical cord syrinx in ~35% (range 20-56%): more common in symptomatic patients
• hydrocephalus in up to 30% 1,3 of cases
• thought to result from abnormal CSF flow dynamics through the central canal of the cord and around the medulla
• skeletal anomalies in ~35% (range 23-45%) 1,3:
• platybasia/basilar invagination
• atlanto-occipital assimilation
• Sprengel deformity
• syndromic associations
• Klippel-Feil syndrome
• Crouzon syndrome
• Hajdu-Cheney syndrome

Question 2

Chiari 1.5

Answer 2

descent >6 mm favours Chiari I malformation and >12 mm suggests Chiari 1.5 malformation

associated findings may include

• posterior angulation of the odontoid process
• hydrocephalus
• crowded small posterior fossa
• syringohydromyelia
• scoliosis

Question 3

Chiari 2

Answer 3

spinal

• syringohydromyelia
• scoliosis
• segmentational anomalies (50%) 7
• Klippel-Feil syndrome
• atlanto-axial assimilation
• diastematomyelia

cerebral

• dysgenesis of corpus callosum
• absent septum pellucidum
• obstructive hydrocephalus
• fenestration of the falx with interdigitated gyri or absent falx; heart shape incisura
• stenogyria/polymicrogyria (probably not the same as polymicrogyia encountered in schizencephaly 7)
• tectal beaking
• cranial vault
• scalloping of petrous temporal bone 3
• enlarged foramen magnum
• Luckenschadel skull
• small posterior fossa
• skeletal
• clubfoot

Question 4

Neurofibromatosis

Answer 4

Skull

1. Dysplastic sphenoid – absent greater wing ± lesser wing (empty orbit) absent posterolateral wall of the orbit. May result in proptosis.
2. Lytic defects in the calvarium, especially in or near the lambdoid suture.
3. Enlargement of foramina
4. Mandibular abnormalities.
5. Enlarged internal auditory meati – due to acoustic neuromas or dural ectasia without associated neuroma.

Brain (see also 12.30)

1. Focal or multifocal ↓ T1W and/or ↑ T2W signal without mass effect, most often in the basal ganglia, cerebellum and cerebral peduncles. No enhancement. May be due to hamartomas. More common in younger patients and in those with an optic glioma. Tendency to regress after teenage years.
2. Tumours
   
   1. Optic tract, chiasm and nerve gliomas (common). 10–30% of optic gliomas are associated with NF-1. The association is higher with optic nerve gliomas, and bilateral optic nerve gliomas are found almost exclusively in NF-1. Optic nerve glioma is not found in NF-2.
   2. Optic nerve sheath meningiomas (rare).
   3. Cranial nerve (V–XII) schwannomas. Frequently multiple and bilateral in NF-2. Acoustic neuromas (schwannomas) are bilateral in at least 90% of NF-2.
   4. Brainstem and supratentorial gliomas.
   5. Intracranial meningiomas – often multiple in NF-2.
   6. Macrocephaly.
   7. Hydrocephalus, of insidious onset – usually due to aqueduct stenosis caused by gliosis but may be secondary to a tumour.
   8. Cerebral and cerebellar calcification. Heavy calcification of the choroid plexuses is rare but classic.
   9. Arachnoid cyst.
   10. Arterial occlusive disease, including moya-moya.

Spine

1. Scoliosis (typically acute and thoracic) and kyphosis.
2. Dural ectasia with posterior scalloping.
3. Absent or hypoplastic pedicles.
4. Spondylolisthesis.
5. Lateral meningocoele (rare).
6. Multiple neurofibromas (enhancing) ± dumbbell. Enlargement of intervertebral foramina. Most common in the cervicothoracic region.
7. Paraspinal plexiform neurofibromas.

Thorax

1. Rib notching, ‘twisted ribbon’ ribs and splaying of ribs.
2. Lung parenchymal disease (20%).
3. Upper zone bullae.
4. Lower zone fibrosis.
5. Mediastinal mass: lateral thoracic meningocoele; neurofibroma.

Gastrointestinal

1. Neurogenic neoplasms – neurofibroma (including plexiform), malignant nerve sheath tumour.
2. Neuroendocrine neoplasms – carcinoid, phaeochromocytoma, paraganglionoma.
3. Non-neurogenic gastrointestinal mesenchymal neoplasms – GIST, leiomyosarcoma.
4. Embryonal tumours – rhabdomyosarcoma, neuroblastoma, Wilms’ tumour.
5. Miscellaneous tumours – gastrointestinal adenocarcinoma, pancreatic and biliary adenocarcinoma.

Appendicular skeleton

1. Overgrowth (limb hemihypertrophy) or, less commonly, undergrowth of long bones.
2. Overtubulation or undertubulation (due to cortical thickening).
3. Anterior and lateral bowing of the tibia with irregular periosteal thickening is common and is usually evident in the first year. It frequently progresses to pseudarthrosis.
4. Pseudarthrosis (tibia; ulna).
5. Intraosseous neurofibromas present as subperiosteal or cortical lucencies with a smooth expanded outer margin.
6. Cortical pressure resorption from an adjacent soft-tissue neurofibroma.
7. Cortical defects may also be due to dysplastic periosteum.
8. Association of non-ossifying fibromas and neurofibromatosis.

Others

1. Soft-tissue neurofibromas and plexiform neurofibromas.
2. Renal artery stenosis or aneurysm.
3. Osteomalacia.