[Clinical characteristics and indications for shunting in patients with idiopathic normal pressure hydrocephalus with brain atrophy (atypical idiopathic normal pressure hydrocephalus)].

PURPOSE: To clarify clinical characteristics of atypical idiopathic normal pressure hydrocephalus (AINPH) and indications for shunt operations.

SUBJECTS AND METHODS: Subjects examined in the present study included 65 patients who satisfied the following 4 diagnostic criteria of AINPH and underwent V.P shunt with Medos type shunt system; set pressure: epidural standard pressure x 13.6 - 20 mmH2O (omission of a figure in the first place). The diagnostic criteria were: 1) no apparent history of intra- or extra-cranial disease; 2) dementia was present as a main complaint; 3) the presence of moderate to severe cerebral atrophy and ventricular enlargement and PVL around the anterior horn on CT scans; 4) normal cerebrospinal pressure and filling of ventricles or subarachnoid space with contrast medium at 24 hours on cisternography. The patients were aged 49-83 with the mean age of 62.9 years; the ratio of male to female was 37:28. They were categorized as shunt-effective (group E: 36 cases) or non-shunt-effective (group NE: 29 cases), and the following parameters in both groups were compared: 1. clinical characteristics: 2. the presence or absence of pressure wave (PW) during preoperative continuous epidural pressure measurement (EDPM) 3. CSF outflow resistance (Ro) 4. preoperative serum alpha-1-antichymotrpsin (alpha-1-ACT) 5. cerebral arteriovenous difference of oxygen content (c-AVDO2) before and after surgery 6. mean cerebral blood flow (mCBF; 99mTc-HMPAO-SPECT) before and after surgery.

RESULTS AND CONCLUSIONS: 1. Group E had a shorter duration between symptom onset and hospital visit (within 16 months and showed hyporoluntary and hyporeactivity as their main complaints associated with gait disturbance; the time course of symptoms was classified as suddenly progressing and fluctuating in many cases. Group NE had a relatively longer duration between symptom onset and hospital visit and showed activeness, wandering, nervousness and quick temper as their main complaints; the time course of symptoms was classified as progressing in many cases. 2. PW-positive cases were all included in group E. but some PW-negative cases were also observed in group E. 3. Ro was significantly higher in group E (p < 0.01), and cases with a Ro value over 20 mmHg/ml/min. were all included in group E. 4. alpha-1-ACT was significantly lower in group E (p < 0.05), and cases with an alpha-1-ACT value over 55 mg/dl were all included in group NE. 5. Although preoperative c-AVDO2 was significantly higher in group E (p < 0.05), cases with a c-AVDO2 value over 8.5 ml% were all included in group NE. c-AVDO2 values were within 5-8.5 ml% in all cases of group E. 6. mCBF significantly increased after surgery in group E (p < 0.001). 7. It was confirmed that cerebral atrophy in group E on AINPH is caused by a cerebral circulation disturbance defined as a cerebral blood flow of penumbra or more due to cerebral arteriosclerosis, etc. 8. A flowchart of indications for shunt surgery for AINPH was prepared based on the results of the present study.