Shunt-Responsive Idiopathic Normal Pressure Hydrocephalus Patient with Delayed Improvement after Tap Test
A 68-year-old man presented to our hospital for evaluation of progressive impairment of gait, balance, and memory. Twenty months earlier, he had developed a short-stepped gait and impaired balance without urinary symptoms. There was progressive deterioration in his gait, and he suffered a few falls recently. His daughter described a 12-month gradual decline in his ability to express himself and, more recently, difficulties in carrying out complex tasks. She reported that his short-term memory had been functionally impaired over the past few months. There was reduced interest in completing instrumental activities of daily living.\nHe had accumulated a 40-pack-year smoking habit, but he had stopped smoking 5 years before presentation. His alcohol intake was restricted to social functions. He did not have a history of stroke or other neurological, metabolic, or neoplastic disorders which might produce dementia symptoms, or parkinsonism, or a history of hospitalization for depression. The patient was positive for diabetes mellitus.\nOn initial examination, the patient's cognitive function was impaired [Korean Mini-Mental State Examination (K-MMSE) score 23 out of 30 and Clinical Dementia Rating Scale 1], and a frontal release sign (palmomental reflex) was present,. He exhibited a short-stride gait with shuffling. The patient had no rigidity in the limbs or neck. His postural reflexes were slightly impaired. Formal neuropsychological evaluation showed a deficit in visuospatial function (copy of the Rey-Osterrieth Complex Figure) and memory (Korean Hopkins Verbal Learning Test and recall and recognition of the Rey-Osterrieth Complex Figure) with frontal dysfunctions (Frontal Assessment Battery). All laboratory test results, including a blood-chemistry panel, complete blood count, thyroid function tests, measurement of vitamin B12 levels, and screening for inflammatory and infectious diseases such as neurosyphilis, were unremarkable. Brain magnetic resonance imaging revealed communicating hydrocephalus with an Evans' ratio of 0.35, and also showed CSF signal void in the cerebral aqueduct and enlargement of the temporal horns of the lateral ventricles (). He showed no evidence of a related antecedent event, such as head trauma, intracerebral hemorrhage, meningitis, or another known cause of secondary hydrocephalus. He was diagnosed as having iNPH following the consensus criteria of Relkin et al..\nThe following several psychological tests and walking tests were applied following the CSFTT. The iNPH Grading Scale (iNPHGS) is a clinician-rated scale for assessing the severity of each of the 3 disorders of iNPH (cognitive impairment, gait disturbance and urinary disturbance). A five-point subscale was used to rate the severity of each fundamental symptom of iNPH after an interview with patients and caregivers. The gait assessment included measurements of time and number of steps on the Timed Up and Go Test (TUG) and the 10-m walking test,. These are valid tests of functional mobility used in many studies to evaluate walking ability,. Both tests were separately performed four times, and the mean score was used.\nAt first hospitalization, a lumbar tap with removal of 40 mL of CSF was performed. Before and after the tap, he was evaluated using the iNPHGS, K-MMSE, TUG, and 10-m walking tests (). Change in gait was evaluated 24 hours after the tap,, while change in cognition and urination was evaluated at one week. All trials were videotaped and analyzed by 2 experienced neurologists. Response to the CSFTT was evaluated using three major scales : iNPHGS, TUG and K-MMSE. The following criteria were used to identify responders : improvement of one point or more on the iNPHGS, more than 10% improvement in time on TUG, or more than 3 points improvement on the K-MMSE. These criteria were frequently used in previous studies,. He did not show sufficient improvement by these criteria, and was judged as a non-responder (). The subjective impression of the patient and his family members, as well as 2 experienced neurologists, regarding overall change in gait after the CSFTT was 'no improvement' within 24 hours. However, his daughter reported that his gait appeared to improve 2 or 3 days after the tap, and again became progressively worse at one week when he visited our clinic for the follow-up cognition test. At that time, the patient and his family wanted conservative treatment with observation instead of operation.\nOver the next 3 months, there was deterioration in his gait and balance again. Trials of levodopa, with dosage up to 600 mg/day, offered no benefit. He suffered multiple falls during the ensuing month. He finally required assistance when walking on an uneven road.\nAt the second hospitalization for the CSFTT, we examined his change in gait over seven days in more detail, considering the findings from the first hospitalization (). It was noticed that his gait began to improve 24 hours after tap and more so 48 hours after tap, and eventually he did show improvement by the criteria : more than 10% improvement in time on TUG. His gait got worse again at one week. The patient and his family were repeatedly asked about their subjective impressions regarding overall improvement after the CSFTT. They agreed that there was temporary improvement 72 hours after tap. The diagnosis was then confirmed as a responder and he underwent shunt surgery. After the operation he improved gradually. The gait difficulties were almost fully resolved, and the balance problem disappeared after 1 month (). The K-MMSE score also improved to 25.