Recent information regarding the nature of bulk cerebrospinal fluid formation and absorption is reviewed, integrated with previous knowledge, and applied to the clinical setting.

Cerebral capillary sequestration and blood‐brain barrier (BBB) permeability to apolipoproteins E2 (apoE2), E3 (apoE3), and E4 (apoE4) and to their complexes with sAβ1–40, a peptide homologous to the major form of soluble Alzheimer's amyloid β, were studied in perfused guinea pig brain. Cerebrovascular uptake of three apoE isoforms was low, their blood‐to‐brain transport undetectable, but uptake by the choroid plexus significant. Binding of all three isoforms to sAβ1–40 in vitro was similar with a KD between 11.8 and 12.9 nM. Transport into brain parenchyma and sequestration by BBB and choroid plexus were negligible for sAβ1–40‐apoE2 and sAβ1–40‐apoE3, but significant for sAβ1–40‐apoE4. After 10 min, 85% of sAβ1–40‐apoE4 taken up at the BBB remained as intact complex, whereas free sAβ1–40 was 51% degraded. Circulating apoE isoforms have contrasting effects on cerebral capillary uptake of and BBB permeability of sAβ. ApoE2 and apoE3 completely prevent cerebral capillary sequestration and blood‐to‐brain transport of sAβ1–40. Conversely, apoE4, by entering brain microvessels and parenchyma as a stable complex with sAβ, reduces peptide degradation and may predispose to cerebrovascular and possibly enhance parenchymal amyloid formation under pathological conditions.

Between 1979 and 1991, spinal arachnoid cysts were found in 11 patients aged 19 months to 18 years (mean age 5 1/2 years). Of the 11 patients, six had a myelomeningocele and one diastematomyelia. The presenting symptoms included radicular pain (one patient), progressive weakness (three), increasing scoliosis (one), worsening spasticity (three), and recurrent urinary tract infections and progressive constipation (one). Two patients showed no symptoms from the spinal arachnoid cyst. The distribution of lesions was as follows: cervicomedullary (one patient), cervical (one), cervicothoracic (two), thoracic (four), lumbar (two), and sacral (one). Four of the 11 arachnoid cysts (all intradural) were located anterior to the spinal cord, three of which were in children with a myelomeningocele. Only two of the cysts were extradural; both were found in the lumbosacral region, and one was associated with diastematomyelia. Eight patients were treated with fenestration and/or resection of the cyst wall. Three patients with anterior cysts were treated with shunts, a cyst-to-pleural space shunt in two and a cyst-to-subarachnoid space shunt in one. All of the patients either improved or exhibited an arrest in the progression of their symptoms. Spinal arachnoid cysts are a treatable cause of progressive neurological deficits and, in this series, were frequently found in patients with neural tube defects.

Background: Congenital central hypoventilation syndrome (CCHS) is a rare disorder affecting central control of breathing. Thus, patients require lifelong assisted ventilation. Diaphragm pacing (DP) may permit decannulation in those who are ventilator dependent only during sleep. Objective: The purpose of this study is to determine if patients with CCHS can be successfully ventilated by DP without tracheostomy. Methods: We reviewed the records of 18 CCHS patients (mean age 19.5 ± 10.1 years; 44% female) who were ventilated by DP only during sleep. Results: Prior to diaphragm pacer implantation surgery, 14 CCHS patients had been using home portable positive pressure ventilation (PPV) via tracheostomy, 1 had been on PPV via endotracheal tube, and 3 had been using noninvasive PPV (NPPV). Of the patients with tracheostomy prior to DP (n = 15), 11 (73%) were decannulated and ventilated successfully by DP without tracheostomy. Of all the patients reviewed (n = 18), 13 (72%) were successfully ventilated by DP without tracheostomy. Obesity prevented successful DP without tracheostomy in 1 patient, and upper airway obstruction prevented success in another patient. Snoring and/or obstructive apneas were present in some patients, but they were improved by diaphragm pacer changes, adenotonsillectomy, and/or use of nasal steroids. Conclusions: DP without tracheostomy can be successfully achieved in patients with CCHS. Snoring and obstructive apneas, when present, can be managed by diaphragm pacer changes and medical therapies. Obesity can pose a challenge to successful DP.