Shingles and the battle of the bulge
By Warren R. Heymann, MD
Sept. 11, 2019
Vol. 1, No. 27
I thought I knew herpes zoster (HZ, shingles) inside and out — from patients’ experiences, my late mother’s herpes zoster ophthalmicus (I could not believe how devastatingly awful she appeared arriving back from Europe!), to my recent vaccination with Shingrix. I just became cognizant of a “new” complication of HZ — (new to me, at least) — the post-herpetic abdominal pseudohernia (PHAP).
Following primary varicella infection, the varicella-zoster virus persists in spinal and cranial nerve ganglia. After reactivation and replication, the virus traverses through sensory nerve fibers associated with the involved ganglion resulting in its classical dermatomal vesicular eruption.
Neurologic complications of HZ are legion, with post-herpetic neuralgia being the most common. Meningoencephalitis, myelitis, cerebrovascular accidents due to cerebral vasculopathy, paresis, and paralysis are potential complications. The Ramsay-Hunt syndrome (RHS) is defined as HZ oticus associated with peripheral facial nerve paresis; other cranial nerves may also be affected. The involvement of the geniculate ganglion in RHS leads to a multiplicity of combination of sensory abnormalities (hearing, taste), motor problems (balance), or disturbances of lacrimal and nasal secretion. (1)
Motor complications of HZ are infrequent, affecting 1-5% of cases. Development of mononeuropathies other than facial nerve palsy are rare. (2)
The differential diagnosis of abdominal bulges includes a hernia or tumor (of the abdominal wall, intra-abdominal, or pelvic), all of which may be detected by imaging. Pseudohernias should also be considered. (3)
What is a pseudohernia? It is a limited protrusion of the abdominal wall without an evident muscle or aponeurotic defect. Relaxation of the anterior abdominal wall will cause it to bulge with increased intra-abdominal pressure. Aside from HZ, the most common cause, pseudohernias have been reported with other radiculopathies associated with diabetes, Lyme disease, polio, and syringomyelia. (4) It has been reported following a rib fracture, presumably causing a denervation injury. (5)
Admittedly, until I read the article by Tirelli et al, (6), I had never heard of a pseudohernia, HZ-related or otherwise. A PubMed search of “herpes zoster and pseudohernia” yielded 21 references, the first being published in 2001 reporting the case of a 78-year-old woman with abdominal-wall muscle paralysis following cutaneous herpes zoster in the T12-L1 dermatomes. An EMG confirmed paralysis, and a CT scan ruled out a fascial defect. The paralysis had completely resolved 1 year later. (7) In the case presented by Tirelli et al, an 82 year-old woman developed PHAP approximately two weeks after HZ of the left T10-T11 dermatomes. She was treated with valacyclovir when she had active vesicles; four months later the PHAP resolved. According to the authors, PHAP is observed in 2% of HZ patients. (I have trouble with this number; perhaps I have missed the diagnosis altogether, or patients do not seek dermatologic evaluation for the condition). PHAP usually occurs in middle-aged to elderly patients, with a male/female ratio of 4/1. Onset of PHAP may accompany the vesicular eruption, or appear shortly thereafter. (6) Zoster sine herpete has also been reported. Imaging (ultrasound, MRI) may be requested to rule out other disorders in the differential diagnosis. The majority of patients with PHAP, approximately 80%, will have complete resolution within a year, with a mean recovery time of about 5 months. (3,6) The pathogenesis of PHAP presumes a polyneuritis and segmental motor neuropathy with secondary muscle denervation, followed by muscle atrophy, leading to muscle weakness of the abdominal wall. (4) PHAP is managed with mechanical support with a corset, pain management, and physical therapy. (5)In conclusion, it is essential that clinicians recognize PHAP. HZ is painful enough without having to undergo unnecessary surgical intervention.
Point to remember: A motor neuropathy associated with truncal herpes zoster may result in abdominal muscle weakness, appearing as a bulge, known as post-herpetic abdominal pseudohernia.
Our expert’s viewpoint
Stephen K. Tyring, MD, PhD, MBA
Clinical professor, Departments of Dermatology, Microbiology & Molecular Genetics and Internal Medicine (Infectious Diseases)
University of Texas Health Science Center, Houston
Motor neuropathies following herpes zoster are infrequent and less commonly recognized than post-herpetic neuralgia. Such motor neuropathies include ptosis and foot drop as well as the unusual complication of post-herpetic abdominal pseudohernia (PHAP). Development of PHAP occurs from viral damage to motor branches of thoracic nerves innervating abdominal muscles. The resulting laxity of these muscles results in a unilateral abdominal bulge. This can produce anxiety in the patient and concern in their physician. Such unease can lead to unnecessary biopsies and other diagnostic procedures as well as to excisional surgical procedures.
Therefore, it is essential that this complication of herpes zoster be recognized. Patients should be reassured that the PHAP will eventually resolve and they should not be concerned for any serious underlying medical problems. Like postherpetic neuralgia, PHAP resolves in a few months. It is not known, however, whether acute antiviral therapy will help PHAP resolve faster. It is speculated that intervention with gabapentin may benefit damage to the motor nerves as it does for sensory nerves and it is sometimes used to treat PHAP.
In conclusion, physicians need to be as aware of the potential of motor neuropathies following herpes zoster as they are of the results of damage to the sensory nerves.
2. Valle-Arcos D, Alonso-Navarro H, Navacerrada F, Jiménez-Jiménez FJ. Peroneal nerve mononeuropathy associated with herpes zoster. A case report. Neurol Sci 2019; 40: 847-850.
3. Eguchi H, Furukawa N, Tago M, Fugjwara M, et al. Temporary unilateral abdominal muscle paralysis due to herpes zoster without typical vesicles or pain. J Gen Fam Med. 2017; 21;18:35-37.
4. Miranda-Merchak, Garcia N, Vealljo R. Varela C. MRI findings of postherpetic abdominal wall pseudohernia: A case report. Clin Imaging 2018; 50:109-112.
5. Butensky AM Gruss LP, Gleit ZL. Flank pseudohernia following posterior rib fracture. J Med Case Rep 2016; 10: 273.
6. Tirelli L, Luna PC, Larralde M. Postherpetic abdominal pseudohernia. Presentation of a clinical case and literature review. Int J Dermatol 2019; 58: 497-499.
7. Zuckerman R. Siegel T. Abdominal-wall pseudohernia secondary to herpes zoster. Hernia 2001; 5: 99-100.
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