An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime.

The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2's Small Carry-on Impactor. The impact produced an artificial crater with a diameter >10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu's surface age.

Post-traumatic leptomeningeal cyst mimicking a skull tumour in an adult.

A 53-year-old female presented with a post-traumatic leptomeningeal cyst manifesting as bulging of the scalp, dizziness and tinnitus. She had known of the bulging of her forehead for about 20 years. She had suffered an injury to the head in childhood. Brain CT revealed a bone cyst associated with a round bone defect in the left frontal bone, bulging of the very thin outer layer and the defective inner layer. She was treated surgically with a diagnosis of skull tumour, but only gray cystic membranous tissue was found. The dural defect was repaired with fascia and the bone defect with bone cement. Bulging of the skull in adults can be caused by a bone cyst originating from a skull fracture.

Distal superior cerebellar artery aneurysm.

A case of an aneurysm arising from the distal portion of the superior cerebellar artery is described. Angiography showed an aneurysm near the internal auditory canal, arising from the medial branch of the superior cerebellar artery associated with hypoplasia of the ipsilateral anterior inferior cerebellar artery and posterior inferior cerebellar artery.

[Clinical manifestation of muco- and pyocele of the sphenoid and ethmoid sinuses (author's transl)].

We, neurosurgeons, frequently encounter patients whose chief compiants are visual disturbance, disorder of the ocular movement, trigeminal neuralgia and/or panhypopituitarism wich have been called as superior orbital fissure syndrome or orbital apex syndrome. Among these, there might be considerably high incidence of mucocele or pyocele of posterior ethmoid sinuses. We have experienced 12 cases of mucocele in past 5 years, which were confirmed by operation. The most reliable method to diagnose mucocele or pyocele at this moment is by the radiogical procedures, and among all, tomogram of the skull is essential. This procedure not only clearly demonstrates the existence of mucocele in a certain sinus but also provides us informations about the surrounding bony stracture. Diagnosis becomes more definite if the epipharyngography demonstrates no filling of postive contrast medium into suspected paranasal sinuses. Treatment of choice for this disease is firstly drainage of mucocele or pyocele by transnasal approach, to avoid postoperative meningitis or brain abscess, and secondarily dissection of the arachnoidal adhesion around the optic chiasm by intracranial approach if it is necessary. Recently, we perform the drainage of mucocel and peeling off of affected mucosa via transnasal route using microsurgical technique. Results are all satisfactory.