Clinical Reasoning: A 75-Year-Old Man With Dementia, Incontinence, and Gait Dysfunction

Idiopathic normal pressure hydrocephalus (iNPH) is a progressive neurological disorder characterized by gait apraxia, cognitive decline, and urinary incontinence. It can be difficult to diagnose iNPH as the symptoms may overlap with other neurodegenerative diseases including cervical spondylotic myelopathy. Cervical spondylotic myelopathy is a progressive degenerative disease in which compression of the cervical spinal cord causes gait disturbances and imbalance, loss of dexterity and strength in the hands, and, at late stages, urinary dysfunction. As with iNPH, increased age is associated with higher incidence and prevalence. Surgical decompression of the cervical spinal cord is the treatment of choice in patients with progressive myelopathy. Accordingly, iNPH and cervical myelopathy may both present with progressive gait impairment and incontinence, especially in the elderly. The case presented here demonstrates that both iNPH and cervical myelopathy may present simultaneously and result in gait disturbances and imbalance in some patients. For patients with suspected iNPH and myelopathic findings on examination, it is prudent to obtain a cervical spine MRI to assess for cervical stenosis. Moreover, cervical stenosis can mask the effect of cerebrospinal fluid diversion in patients with comorbid iNPH and cervical myelopathy. Therefore, the differential for patients who have symptomology suggestive of iNPH should include cervical spine myelopathy, with considerations for possible cervical decompression in addition to placement of a ventriculoperitoneal shunt.


Introduction
The case presented here demonstrates that both idiopathic normal pressure hydrocephalus (iNPH) and cervical myelopathy may present simultaneously and result in gait disturbances and imbalance in some patients. For patients with suspected iNPH and myelopathic findings on examination, a cervical spine MRI should be considered to assess for cervical stenosis. Cervical stenosis can mask the effect of CSF diversion in patients with comorbid iNPH and cervical myelopathy.

Case Presentation
A 75-year-old man presented with progressive deterioration in gait and balance over a twoyear period. One year after symptom onset, he was diagnosed with Parkinson's disease and was 1 2 3 2 Open Access Case Report DOI: 10   The differential diagnosis of progressive gait apraxia, mild cognitive impairment, and urge incontinence includes iNPH, cervical spondylotic myelopathy, typical and atypical parkinsonism, hip osteoarthritis, and combinations of these. As described previously, the brain MRI was consistent with iNPH, but the patient had an equivocal response to the high-volume lumbar puncture. The cervical spine MRI revealed diffuse degenerative changes with moderate stenosis at C5-C6, which, in combination with the upper motor neuron findings on examination (even without weakness or loss of dexterity in the hands), suggested cervical myelopathy. The patient had already been treated with carbidopa/levodopa, but without any benefit. Finally, plain radiographs revealed advanced osteoarthritis of the hips and sacroiliac joints, but this diagnosis did not explain the patient's cognitive impairment or urinary symptoms. Based on the underwhelming response to high-volume CSF removal and mobile spondylolisthesis in the cervical spine, a flexion-extension MRI of the cervical spine was pursued, which demonstrated slight progression of the canal effacement at C5-C6 in extension but, surprisingly, also demonstrated dynamic compression of the spinal cord at C4-C5 ( Figure 1D).
Anterior cervical discectomy and fusion (ACDF) at C4-C5 and C5-C6 was performed, without complication, to decompress the cervical spinal cord. He continued to suffer progressive deterioration of his gait and balance over the ensuing year, however, and therefore returned for repeat lumbar tap test. Prior to this second high-volume lumbar puncture, the patient took 31.1 seconds on average to walk 10 meters (SD: 3.6 seconds; n = 4) and an average of 7.6 steps per 180˚ turn. The opening pressure of the lumbar puncture was 194 mmH 2 O. After removing 30-mL CSF, it took the patient an average of 16.0 seconds to walk 10 meters (SD: 0.8 seconds; n = 4) and 5.0 steps to turn 180˚. The difference in time to complete a 10-meter walk (Video 1) before and after lumbar puncture was statistically significant (p < 0.01), as was the number of steps per 180˚ turn (p < 0.01), both determined using a two-tailed Student's t-test. Based on this clear response to temporary CSF removal, the patient underwent placement of a right parietal ventriculoperitoneal shunt. Three months after shunting, the patient was no longer using a walker and just used a cane when outside the house and had not fallen.

Discussion
INPH is a progressive neurological disorder characterized by gait apraxia, cognitive decline, and urinary incontinence [1]. Neuroimaging demonstrates ventriculomegaly despite normal lumbar puncture opening pressure [2]. The incidence of iNPH is 0.5 to 5.5 per 100,000 people per year and increases as a function of age [3,4]. It can be difficult to diagnose iNPH as the symptoms may overlap with other neurodegenerative diseases [5]. Treatment for iNPH is prolonged CSF diversion through shunting, which is most effective in ameliorating gait dysfunction, although as many as 20% of shunted patients fail to achieve full resolution of gait abnormalities [6]. The decision as to whether a patient is a good candidate for shunting can be determined by their response to high-volume lumbar tap [7].
Cervical spondylotic myelopathy is a progressive degenerative disease in which compression of the cervical spinal cord causes gait disturbances and imbalance, loss of dexterity and strength in the hands, and, at late stages, urinary dysfunction [6,8]. As with iNPH, increased age is associated with higher incidence and prevalence. Surgical decompression of the cervical spinal cord is the treatment of choice in patients with progressive myelopathy [9]. Accordingly, iNPH and cervical myelopathy may both present with progressive gait impairment and incontinence, especially in the elderly [10].
The case presented here demonstrates that both iNPH and cervical myelopathy may present simultaneously and result in gait disturbances and imbalance in some patients. For patients with suspected iNPH and myelopathic findings on examination, it is prudent to obtain a cervical spine MRI to assess for cervical stenosis. Moreover, cervical stenosis can mask the effect of CSF diversion in patients with comorbid iNPH and cervical myelopathy. This phenomenon may be, in part, why up to 20% of patients with iNPH fail to achieve full gait resolution after shunting. Therefore, the differential for patients who have symptomology suggestive of iNPH should include cervical spine myelopathy, with considerations for possible cervical decompression in addition to placement of a ventriculoperitoneal shunt.

Conclusions
For patients with suspected iNPH and myelopathic findings on examination, it is prudent to obtain a cervical spine MRI to assess for cervical stenosis. The differential for patients who have symptomology suggestive of iNPH should include cervical spine myelopathy, with considerations for possible cervical decompression in addition to placement of a ventriculoperitoneal shunt.

Additional Information Disclosures
Human subjects: Consent was obtained by all participants in this study.

Conflicts of interest:
In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.