Polyneuropathy complicating the diagnosis of normal pressure hydrocephalus: case report and review of literature.

Abstract: Polyneuropathy is a rare association of normal pressure hydrocephalus (NPH) and may complicate the diagnosis of both diseases. We describe a patient with NPH who presented with acute polyneuropathy. The patient was initially thought to have Guillain-Barre disease (GBS). Early consideration of NPH in patients presenting with acute polyneuropathy could result in prompt diagnosis and treatment of NPH.

Key Words: normal pressure hydrocephalus, polyneuropathy, Guillain-Barre

Case Report

A 72-year-old African-American male presented to our hospital with complaints of generalized weakness of all extremities; however, the weakness was more profound in the lower extremities. The weakness had increased during the 4 days preceding admission, resulting in an inability to ambulate. According to a family member, the patient had been increasingly forgetful during the 4 months before admission. The patient had no history of falls, vertigo or urinary or fecal incontinence. He denied any alcohol, tobacco or illicit drug use, and there was no history of diabetes mellitus.

On presentation, the patient was alert and oriented; his speech was clear. Short-term memory was intact; however, he had some difficulty in recalling long-term events. The strength in both lower limbs was 1/5; upper limb strength was 4/5. Reflexes were absent bilaterally in the lower limbs, but preserved in the upper limbs. The lower limbs showed flaccid paralysis. The sensory system, cranial nerves, and tested cerebellar functions were all grossly intact. Gait could not be assessed because the patient was unable to walk.

His complete blood count and basic metabolic profile was normal except for a reduced potassium of 3.2. In view of his clinical findings and history, a diagnosis of Guillain-Barre syndrome was initially postulated.

A nerve conduction study of the lower limbs study was suggestive of significant demyelinating polyneuropathy. (Fig. 1) There was also mild left sensory polyneuropathy. The patient underwent a CT scan of the brain which revealed significant atrophy and dilated ventricles (Fig. 2). The ventricular size was out of proportion to the amount of atrophy. A lumbar puncture showed the opening pressure was near normal at 22 cm of [H.sub.2]O (normal 10-20 cm of [H.sub.2]O). After removal of approximately 30 cc of clear cerebrospinal fluid (CSF), the patient had improvement to 4/5 of his bilateral lower limb strength, and reflexes which were absent initially were 2/4 bilaterally. The remainder of the CSF findings, including the protein level, was normal. In view of the above-mentioned findings and with the improvement post lumbar puncture, it was thought that the patient had normal pressure hydrocephalus with superimposed polyneuropathy.

The patient underwent a ventriculoperitoneal shunt and, within 24 hours of its placement, had significant improvement in gait and strength. In view of his clinical improvement, we did not repeat his nerve conduction study. The patient demonstrated improved long-term memory; however, he was transferred to a rehabilitation center before precise objective testing could be performed.

Discussion

We describe a patient with simultaneous acute polyneuropathy and NPH. As our patient illustrates, the coexistence of these diseases can complicate the diagnoses. In NPH, the reflexes are preserved, and there is no acute loss of strength. (1) In contrast, our patient demonstrated absent reflexes and acute loss of strength of the lower limbs due to the coexisting acute polyneuropathy.

We performed a MEDLINE literature search for case reports of polyneuropathy in cases of NPH. The search terms used were: polyneuropathy and normal pressure hydrocephalus; Guillain-Barre syndrome and normal pressure hydrocephalus; and normal pressure hydrocephalus.

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The frequency and pathophysiology of simultaneous acute polyneuropathy and NPH are not known. For example, in the case series by Tisell et al, (3) none of the patients had demyelinating polyneuropathy. Kereschi and colleagues (5) reported a case of NPH associated with GBS in which they postulated the presence of NPH secondary to high CSF protein due to GBS. Accordingly, in select patients, the coexistence of NPH and polyneuropathy could be due to the circulation of still unidentified molecules simultaneously affecting both neuron and CSF metabolism. Identification of such patients and appropriate studies are necessary to support this idea.

Idiopathic NPH is characterized by the triad of ataxic or apraxic gait disturbance, dementia and urinary incontinence. (1,2) In one series, ataxia was the debut symptom in 44% of the patients. (3) NPH is postulated to be caused by an obstruction of the normal flow of CSF and delayed absorption into the venous system. The indolent nature of this process results in enlarged lateral ventricles but relatively little increase in CSF pressure. (1) The major diagnostic challenge is to differentiate NPH from cerebral atrophy and deep white matter ischemia, both far more common causes of the clinical triad than NPH. This is differentiated by the ventricular enlargement observed with the degree of enlargement of the cortical sulci. (4)

In NPH, there is sometimes a transient improvement in gait or cognition following lumbar puncture with removal of 30 to 50 mL of CSF (CSF tap test) as demonstrated by our patient. This test has a high sensitivity but low specificity. (2,6) The treatment of choice for patients with NPH is a ventricular shunting procedure, (1) which normally leads to a greater improvement in gait than cognition. (7) However, patients with idiopathic NPH who show clinical improvement in any symptom after lumbar drainage are likely to show significant long-term improvement in memory after ventriculoperitoneal shunt. (7)

Conclusion

To the best of our knowledge, this is the first reported association in the English literature of acute polyneuropathy and NPH. Polyneuropathy is a rare association of NPH. Patients with acute extremity weakness, absent reflexes and symptoms of cognitive, gait and other urinary disturbances should be evaluated for concurrent NPH.

References

1. Verrees M, Selman WR. Management of normal pressure hydrocephalus. Am Fam Physician 2004;70:1071-1078.

2. Ishikawa M. Guideline Committee for Idiopathic Normal Pressure Hydrocephalus, Japanese Society of Normal Pressure Hydrocephalus: clinical guidelines for idiopathic normal pressure hydrocephalus. Neurol Med Chir (Tokyo) 2004;44:222-223.

3. Tisell M, Tullberg M, Hellstrom P, et al. Neurological symptoms and signs in adult aqueductal stenosis. Acta Neurol Scand 2003;107:311-315.

4. Fishman RA, Dillon WP. Normal pressure hydrocephalus: new findings and old questions. AJNR Am J Neuroradiol 2001;22:1640-1641.

5. Kereschi S, Soria E, Schlagenhauff RE. Normal pressure hydrocephalus; associated with Guillain-Barre syndrome. N Y State J Med 1981;81:1361-1363.

6. Kahlon B, Sundbarg G, Rehncrona S. Comparison between the lumbar infusion and CSF tap tests to predict outcome after shunt surgery in suspected normal pressure hydrocephalus. J Neurol Neurosurg Psychiatry 2002;73:721-726.

7. Duinkerke A, Williams MA, Rigamonti D, et al. Cognitive recovery in idiopathic normal pressure hydrocephalus after shunt. Cogn Behav Neurol 2004;17:179-184.

Jagdish S. Nachnani, MD and Alan R. Salkind, MD

From the Department of Internal Medicine, University of Missouri, Kansas City School of Medicine, Kansas City, MO.

Reprint requests to Alan Salkind, MD, University of Missouri-Kansas City, School of Medicine, 4 Green Unit, 2411 Holmes Street, Kansas City, MO 64108-2792. Email: [e-mail]

Accepted March 8, 2006.

RELATED ARTICLE: Key points:

* Acute polyneuropathy is a rare association of normal pressure hydrocephalus (NPH) and may complicate the diagnosis in these patients.

* Early consideration of NPH in patients presenting with acute polyneuropathy could result in earlier diagnosis and treatment of NPH.